How to get Scanner of HP Envy 4504 to work?

Hi,

I have a HP Envy 4504 all in one device which I want to use over my home network. Printing is fine, but scanning is not. :-(
Operating system: Kubuntu 14.04 LTS with KDE 4.14.2. It is an 64 bit OS.

Everytime I try to start a scan in the HP Device Manager, Xsane tries to start, but just comes up with a failure message

"Error while opening device 'hpaio:/net/ENVY_4500_series?ip=192.168.0.104': invalid argument"

Here is what I did:

Installed the latest version of HPLIP from Sourceforge (HPLIP 3.15.2) and did the recommended automatic install. Afterwards I set the printer up, as recommended, with

hp-setup

in Terminal. I used the setup-method for a network printer with a temporary USB-connection and everything went fine. After the setup was finished, the setup tool told me to run

hp-setup 192.168.0.104 (because thats the IP-address, the printer got)

There also everything went fine, but it complained:

can not get ibus-daemon's address

A short google-ing revealed that ibus needs to be installed. So I did this and now I also can see the catridge information of the printer over the network. But scanning still does not work.

Here is what hp-check -t says:

~$ hp-check -t
Saving output in log file: /home/steffen/hp-check.log

HP Linux Imaging and Printing System (ver. 3.15.2)
Dependency/Version Check Utility ver. 15.1

Copyright (c) 2001-15 Hewlett-Packard Development Company, LP
This software comes with ABSOLUTELY NO WARRANTY.
This is free software, and you are welcome to distribute it
under certain conditions. See COPYING file for more details.

Note: hp-check can be run in three modes:
1. Compile-time check mode (-c or --compile): Use this mode before compiling the HPLIP supplied tarball (.tar.gz or .run) to determine if the proper
dependencies are installed to successfully compile HPLIP.
2. Run-time check mode (-r or --run): Use this mode to determine if a distro supplied package (.deb, .rpm, etc) or an already built HPLIP supplied tarball
has the proper dependencies installed to successfully run.
3. Both compile- and run-time check mode (-b or --both) (Default): This mode will check both of the above cases (both compile- and run-time dependencies).

Check types:
a. EXTERNALDEP - External Dependencies
b. GENERALDEP - General Dependencies (required both at compile and run time)
c. COMPILEDEP - Compile time Dependencies
d. [All are run-time checks]
PYEXT SCANCONF QUEUES PERMISSION

Status Types:
    OK
    MISSING - Missing Dependency or Permission or Plug-in
    INCOMPAT - Incompatible dependency-version or Plugin-version

---------------
| SYSTEM INFO |
---------------

 Kernel: 3.13.0-46-generic #79-Ubuntu SMP Tue Mar 10 20:06:50 UTC 2015 GNU/Linux
 Host: Turbo-X
 Proc: 3.13.0-46-generic #79-Ubuntu SMP Tue Mar 10 20:06:50 UTC 2015 GNU/Linux
 Distribution: ubuntu 14.04
 Bitness: 64 bit

-----------------------
| HPLIP CONFIGURATION |
-----------------------

HPLIP-Version: HPLIP 3.15.2
HPLIP-Home: /usr/share/hplip
HPLIP-Installation: Auto installation is supported for ubuntu distro 14.04 version

Current contents of '/etc/hp/hplip.conf' file:
# hplip.conf. Generated from hplip.conf.in by configure.

[hplip]
version=3.15.2

[dirs]
home=/usr/share/hplip
run=/var/run
ppd=/usr/share/ppd/HP
ppdbase=/usr/share/ppd
doc=/usr/share/doc/hplip-3.15.2
html=/usr/share/doc/hplip-3.15.2
icon=/usr/share/applications
cupsbackend=/usr/lib/cups/backend
cupsfilter=/usr/lib/cups/filter
drv=/usr/share/cups/drv/hp
bin=/usr/bin

# Following values are determined at configure time and cannot be changed.
[configure]
network-build=yes
libusb01-build=no
pp-build=no
gui-build=yes
scanner-build=yes
fax-build=yes
dbus-build=yes
cups11-build=no
doc-build=yes
shadow-build=no
hpijs-install=no
foomatic-drv-install=no
foomatic-ppd-install=no
foomatic-rip-hplip-install=no
hpcups-install=yes
cups-drv-install=yes
cups-ppd-install=no
internal-tag=3.15.2
restricted-build=no
ui-toolkit=qt4
qt3=no
qt4=yes
policy-kit=no
lite-build=no
udev_sysfs_rules=no
hpcups-only-build=no
hpijs-only-build=no

Current contents of '/var/lib/hp/hplip.state' file:
[plugin]
installed = 1
eula = 1
version = 3.15.2

Current contents of '~/.hplip/hplip.conf' file:
[upgrade]
notify_upgrade = true
last_upgraded_time = 1426839681
pending_upgrade_time = 0
latest_available_version = 3.15.2

[settings]
systray_visible = 0
systray_messages = 0

[last_used]
device_uri = "hp:/net/ENVY_4500_series?ip=192.168.0.104"
printer_name =
working_dir = .

[commands]
scan = /usr/bin/xsane -V %SANE_URI%

[refresh]
rate = 30
enable = false
type = 1

[polling]
enable = false
interval = 5
device_list =

[fax]
voice_phone =
email_address =

[installation]
date_time = 20.03.2015 09:44:27
version = 3.15.2

 <Package-name> <Package-Desc> <Required/Optional> <Min-Version> <Installed-Version> <Status> <Comment>

--------------------------
| External Dependencies |
--------------------------

 gs GhostScript - PostScript and PDF language interpreter and previewer REQUIRED 7.05 9.10 OK -
 scanimage scanimage - Shell scanning program OPTIONAL 1.0 1.0.23 OK -
 xsane xsane - Graphical scanner frontend for SANE OPTIONAL 0.9 0.998 OK -
 cups CUPS - Common Unix Printing System REQUIRED 1.1 1.7.2 OK 'CUPS Scheduler is running'
 policykit PolicyKit - Administrative policy framework OPTIONAL - 0.105 OK -
 network network -wget OPTIONAL - 1.15 OK -
 avahi-utils avahi-utils OPTIONAL - 0.6.31 OK -
 dbus DBus - Message bus system REQUIRED - 1.6.18 OK -

-------------------------
| General Dependencies |
-------------------------

 libcrypto libcrypto - OpenSSL cryptographic library REQUIRED - 1.0.1 OK -
 python-dbus Python DBus - Python bindings for DBus REQUIRED 0.80.0 1.2.0 OK -
 reportlab Reportlab - PDF library for Python OPTIONAL 2.0 3.0 OK -
 python-notify Python libnotify - Python bindings for the libnotify Desktop notifications OPTIONAL - - OK -
 pyqt4 PyQt 4- Qt interface for Python (for Qt version 4.x) REQUIRED 4.0 4.10.4 OK -
 python-xml Python XML libraries REQUIRED - 2.1.0 OK -
 libusb libusb - USB library REQUIRED - 1.0 OK -
 cups-image CUPS image - CUPS image development files REQUIRED - 1.7.2 OK -
 libnetsnmp-devel libnetsnmp-devel - SNMP networking library development files REQUIRED 5.0.9 5.7.2 OK -
 sane-devel SANE - Scanning library development files REQUIRED - 1.0.23 OK -
 pil PIL - Python Imaging Library (required for commandline scanning with hp-scan) OPTIONAL - 1.1.7 OK -
 python2X Python 2.2 or greater - Python programming language REQUIRED 2.2 2.7.6 OK -
 pyqt4-dbus PyQt 4 DBus - DBus Support for PyQt4 REQUIRED 4.0 4.10.4 OK -
 libjpeg libjpeg - JPEG library REQUIRED - - OK -
 libpthread libpthread - POSIX threads library REQUIRED - 2.19 OK -
 python-devel Python devel - Python development files REQUIRED 2.2 2.7.6 OK -
 cups-devel CUPS devel- Common Unix Printing System development files REQUIRED - 1.7.2 OK -
 sane SANE - Scanning library REQUIRED - 1.0.23 OK -

---------------
| COMPILEDEP |
---------------

 libtool libtool - Library building support services REQUIRED - 2.4.2 OK -
 gcc gcc - GNU Project C and C++ Compiler REQUIRED - 4.8.2 OK -
 make make - GNU make utility to maintain groups of programs REQUIRED 3.0 3.81 OK -

----------------------
| Python Extentions |
----------------------

 cupsext CUPS-Extension REQUIRED - 3.15.2 OK -
 hpmudext IO-Extension REQUIRED - 3.15.2 OK -

-----------------------
| Scan Configuration |
-----------------------

 scanext Scan-SANE-Extension REQUIRED - 3.15.2 OK -
 hpaio HPLIP-SANE-Backend REQUIRED - 3.15.2 OK 'hpaio found in /etc/sane.d/dll.conf'

-----------------------
| Other Dependencies |
-----------------------

------------------------------
| DISCOVERED SCANNER DEVICES |
------------------------------

No Scanner found.

--------------------------
| DISCOVERED USB DEVICES |
--------------------------

No devices found.

---------------------------------
| INSTALLED CUPS PRINTER QUEUES |
---------------------------------

Brother_DCP-195C
----------------
Type: Unknown
Device URI: usb://Brother/DCP-195C?serial=BROL1F226524
PPD: /etc/cups/ppd/Brother_DCP-195C.ppd
PPD Description: Brother DCP-195C CUPS
Printer status: printer Brother_DCP-195C is idle. enabled since Do 19 Mär 2015 16:49:29 CET
warning: Printer is not HPLIP installed. Printers must use the hp: or hpfax: CUPS backend for HP-Devices.

ENVY_4500
---------
Type: Printer
Device URI: hp:/net/ENVY_4500_series?ip=192.168.0.104
PPD: /etc/cups/ppd/ENVY_4500.ppd
PPD Description: HP Envy 4500 Series, hpcups 3.15.2
Printer status: printer ENVY_4500 is idle. enabled since Fr 20 Mär 2015 09:35:18 CET
Communication status: Good

--------------
| PERMISSION |
--------------

-----------
| SUMMARY |
-----------

Missing Required Dependencies
-----------------------------
None

Missing Optional Dependencies
-----------------------------
None

Total Errors: 0
Total Warnings: 1

Done.

It would be really awesome, if you could help me with this, because I really don't know what is wrong here.

Thanks & regards
Steffen