Oculus Quest can display a black screen when trying to launch the MeetinVR app or while running it.
There are 2 scenarios we are familiar with:
Network ports are closed, making MeetinVR unable to connect to the Internet. Here you can find the list of Opening firewall ports for using MeetinVR.
Oculus Quest runs out of memory and MeetinVR crashes. You can follow this article for guidelines on how to prevent Oculus Quest running out of memory while using MeetinVR.