Invitations links I create do not work

Participants receive error messages when they use invitation links to my meetings. They receive error messages, either "Host is currently attending another meeting" or "Meeting-ID incorrect/defective". In a nutshell, participants can't join my meetings. In return I have no trouble joining Zoom meetings hosted by others.

I updated Zoom and re-installed the app to no avail. 

Has anyone experienced this before and can point me to a solution?

Regards, Ina