I'll do my best. I can't assume you did the right thing, so if I ask any questions that you don't like, please don't get angry at me.
That would not be expected to work. Very few Macs paired at random would have the exact same screen resolution and DPI settings.
I saw no evidence that you replaced the picture. Your image is exactly the same as mine. That's very unexpected. That means there's a 90% chance you did not replace the image. Until your image is slightly different from mine, at least by one pixel, I have to be open to the possibility that you did not replace it.
That could also be your problem. There are two images in the macro and you said you only replaced one.
One simpler method to troubleshoot this is for you to create a macro with a single Find Image action. In that action you need to insert this bitmap which you yourself must capture from your own screen (from your own menu bar when KM Editor is the front application):
And your macro will actually look like this: (be careful to match the options exactly as shown)
Then you run the action, and see if your menu bar turns green. If it does, you're doing something right. If it doesn't, you are doing something wrong.