Well, I have 38 other repositories enabled, just tried another one without any problems. I cannot remember having problems with other repositories.

This problem occurred several weeks ago, restarting Warehouse nor rebooting the phone didn't help.

So I assume it's something wrong in the combination of my Warehouse-Installation and the MeeCast-Repo. However I don't have a clue what's wrong.

Finally I tried it on the command line via ssu addrepo, pkcon install which worked.
Warehouse shows that MeeCast 0.9.16-1 is installed but does still present the option "enable repository"