After new installation no app management

after an upgrade failure I installed Nextcloud from the scratch. After all I cannot manage the apps. When I selcet Apps I get an error: An error occurred during the request. Unable to proceed.
I tried the new installation 2 times with the same result.
What can I do?

why did you delete the underlaying template here in which we ask informations about the problematic system?

So right now nobody except for you knows about the setup of your instance. How could anyone help then?

Additional to the infos required it might be interesting getting to know on which hardware you installed your instance as well as: under a 32bit or 64bit OS?

Hello Jimmy,
sorry for deletion of the required infos.
I installed the instance on the server of my provider and now I think that is a problem there because on the test installation of my computer the app management works. I am now in contact with my provider.