Why just Mac Client 2.3.0rc1 (build 4) works, no other?

I use two Macbooks with macOS Sierra. I tried to use newer stable versions of nextcloud Desktop app, but it doesn’t work. It always appear the error message after enter the Nextcloud Server URL. The only one which works is: Mac Client 2.3.0rc1 (build 4).
I don’t know what the problem is with all other versions.
Any ideas?

If you have the error messages, you can report them to the bugtracker: https://github.com/nextcloud/client_theming/issues

its a pity, there are no error messages. I also miss them.