Unable to add connectors on any channel

My patience is run out. The issue is existing more than 7 days, no solution. So I also did open an MS ticket. I did wrote every piece of information. Unfortunately, when first Microsoft called me, I was unable to speak with them, because I was at a meeting. So they wrote me some instructions to try. I explicitly wrote down that the problem can be reproduced via web but these tips I got:

Hint: it did not solve my issue, but you can try.

1. Compatibility mode

Right-click the MS Team icon on the taskbar then select quit.

- Then right-click the MS Team icon on the desktop > select properties > Under the compatibility tab, check the "Run this program in compatibility mode for" option then select Windows 7 from the dropdown list

- Right-click the MS Team shortcut on the desktop > select run as administrator.

2. Clear cache

Fully exit the Microsoft Teams desktop client. To do this, either right click Teams from the Icon Tray, select ‘Quit’. Or run Task Manager and fully kill the process.

Go to File Explorer, and type in %appdata%\Microsoft\teams.

Once in the directory, delete any file in the following folders:

%appdata%\Microsoft\teams\application cache\cache

%appdata%\Microsoft\teams\blob_storage

%appdata%\Microsoft\teams\Cache

%appdata%\Microsoft\teams\databases

%appdata%\Microsoft\teams\GPUcache

%appdata%\Microsoft\teams\IndexedDB

%appdata%\Microsoft\teams\Local Storage

%appdata%\Microsoft\teams\tmp

3. Reinstall Teams