RTMP Output Stopped

Hi There

I’m using Manycom ios on an Ipad and Iphone to livestream meetings using my Vimeo account

The RTMP address is correct as is the streamkey.
When I go to Start stream I get the message RTMP Output stopped
connection failed.

The devices are on the same network, can see each other. Other streaming platforms work fine on the network

Any tips would be greatly appreciated.