Bug/Issue Smapi 2.11.1 Installing issue

I intended to upgrade my Smapi Edition, but it hasn't worked since.
I deinstalled all Smapi Versions afterwards, aswell as all Mods. The Game now runs normal but without mods.
Everytime I try to install this message shows up (see bottom).

Here are the things I tried so far:
- Use as administrator
- closed all Steam applications
- checked for errors in Steam, missing data was replaced by steam

I can't link any error messages since the %appdata%\StardewValley doesn't have a ErrorLogs archive.