Cannot verify an object on screen

URL path1 = "Sikuli/test1.png";

... is not valid Java: a String cannot be converted to an URL

Finder() and Finder.find() accept valid path strings.
Valid means, that the image file can be loaded from the given path: absolute paths always work if valid.

Relative paths can only be evaluated against a valid ImagePath.

In your case it would give:
String path1 = "Sikuli/test1.png";
Finder finder = new Finder(path1);

[error] ImagePath: find: not in ImagePath: Sikuli/test1.png
[debug] ImagePath: BundlePath: --- not set ---
[error] java.lang.NullPointerException: Cannot invoke "java.awt.image.BufferedImage.getType()" because "bImg" is null

I do not know, where your folder "Sikuli" is in your file system, but something like this would help:
ImagePath.setBundlePath("/..../somewhere/Sikuli/");

and then:
String path1 = "test1.png";
String path2 = "test2.png";
Finder finder = new Finder(path1);
finder.find(path2);

if (finder.hasNext()) {
System.out.println("found");
}

would work.

I recommend to use SikuliX 2.0.5 and Java 8+ 64-Bit, because earlier versions are no longer supported in case of problems.

Thank you for your answer. I really have no issues with image paths, I know that because I have already save 'em as files to check this situation out, when debugging. I think my issue is with the different screen sizes. I take a screenshot from a screen and compare it to another image which is different resolution. I take my images files as follow, I am posting the full code now I have my laptop with me :)

public static boolean imageExist(String kind, String fileName, int secondsWait) {
        Settings.MinSimilarity = Double.parseDouble(SerenityProperties.read("sikuli.similarity"));

        //Object to be found
        URL path = SikuliRemote.class.getClassLoader().getResource("Sikuli/" + kind + "/" + fileName);
        String absolutePath = path.getPath();

        try {
            File screenshotFile = ((TakesScreenshot) Serenity.getDriver()).getScreenshotAs(OutputType.FILE);
            Finder finder = new Finder(screenshotFile.getPath());

            finder.find(absolutePath);
            if (finder.hasNext()) {
                System.out.println("Object found.");
                return true;
            }
        } catch (Exception e) {
            SerenityUtilities.logMessage("Cannot get a screenshot");
        }

        return false;
    }

I will do some more experiments and will come back.

ok, not really fair to give invalid/incomplete information. costs my time.

The image to search must fit into the image to search in.