Zoom call keep disconnecting

Folks,

My son has a peculiar problem logging in zoom. It keeps disconnecting frequently. The issue is very annoying. He is unable to attend any classes. 

We have tried using different network connections wifi or cellular and different network providers. 

We also tried using different devices. The end result is the same.

We have tried other zoom accounts for meetings on the same devices and networks, and we dont see any issue. 

Has anyone seen this issue? Any help?