@topknotch - thanks for the help. I looked at your configuration and in hte module settings the list was deselected. I don't know how this happaned, but it seems that you first checked the correct list, then you added your fields, then you changed the list to nothing? And that's why cmc couln't subscribe you, because no list was selected in the backend.
After selecting the list it is now working. So for other people running in that issue -> go to your module settings and make sure that listid is selected!
404: The requested resource could not be found.
7 months 3 weeks ago #35803
aha, I probably did this as I had it on a test domain and when I removed the data I forgot to re add the new list to the module!
Thank you very much for your support and I hope others with this problem were just being stupid like me!