Hi Faisal.Sharif!
Does this issue persist all the time?
Can desktop client user make A/V call to Android SFB user normally?
Considering this issue related to mobile device, it may have some issues in your edge server. You could try to check if there are any event error logs in the Edge and FE Server at first. Then you can check your edge server deployments such as DNS records
and certificate on edge server.


Also please make sure you have opened the following ports on A/V edge servers.

Best Regards,
Jimmy Yang
Please remember to
mark the replies as answers if they helped. If you have feedback for TechNet Subscriber Support, contact
tnsf@microsoft.com.