iPhone app display "Umstable network, tap to reconnect"

[kng]

I am using a iPhone iOS 17.7.2 with three uk.

When I was using the APP, I am unable to join meeting with 4G/5G.  But I can join meeting via browser under 4G/5G.  When I turn on VPN on top of 4G/5G, I can also join meeting with the APP.

When I was using WiFi, I am able to join meeting with APP.

any suggestion?

[storyhub]

It looks like you answered your own question. Trying to stream over ANY radio based network (cellular and WiFi are radio systems)  will always have stability issues. An iPhone uses very little transmission power for cellular or WiFi so distance to the receiver will drastically change the signal quality.

[kng]

The cellular signal is perfect, all other internet activity goes well.  It can't answer why it works after I turned on VPN?  And the situation happen for few days.  Is it a program bugs or something about DNS settings for zoom?