I'm facing the same issue with Jio network and Firebase Realtime Database. The listener doesn't trigger onDataChange() or onCancelled() — it just hangs.

Tested fixes:

• Changing APN from IPv4/IPv6 to IPv4 works (but not ideal for users).

• Private DNS (like dns.google) on device doesn’t help.

• VPN or router-level DNS change (to 8.8.8.8) fixes it.

Workaround:
I now use a Firebase Cloud Function as a proxy to access Realtime Database. This works reliably even on Jio.