Unfortunately, I can rarely use the Nichenfinder because it is usually not available and the website only loads.
I also had contact with the support and here I was told that they know about the problem and the error will be fixed.
That was about 10-14 days ago, unfortunately, the problem still exists and my 60-day return ends now and I can do with the app so unfortunately nothing.
If the problem was fixed, I would get the app again and test further.