It is impossible to resolve any technical problems that you may have at the time of a virtual Café without disrupting the event.
So having installed Zoom, it is essential that you test your system for any video/audio problems before your first Café and to familiarize yourself a little with the system.
To help with this, I run Zoom check-out meetings where you can join an informal Zoom session hosted by me to test your hardware, learn a little about Zoom and meet other Zoom users.
These sessions last for one hour and you can drop in and drop out at any time.
The next Zoom check-out meeting is shown below: