Check
System requirements
Check with your system administrator that the system requirements are met.
Network configuration
Often, problems with the network configuration manifest themselves in such error conditions. Please check the article I keep having connection difficulties during a meeting.
Browser
Chrome
Google Chrome or Chromium browsers do not currently offer specific screen-sharing settings.
Mozilla Firefox
If you want to share the screen in a meeting, Mozilla Firefox offers a popup window for this purpose. However, if you have selected "Do not allow" here, then this popup window will not appear the next time you try to share the screen. You will then have to adjust the settings manually:
Permissions for meetings.procall.de → delete this permission and ask again. Then refresh the page with F5 or "Refresh".
Operating system settings
Apple macOS from Catalina
Follow the instructions in the following documentation appropriate to the operating system to give permission to the appropriate browser: https://support.apple.com/en-us/guide/mac-help/mchld6aa7d23/mac
Microsoft Windows
Windows operating systems currently do not offer specific settings for screen sharing.
Further procedure