You may still use the cam2cam feature in "video only" mode and you will be able to hear the performer, but they won't be able to hear your sound.
This issue has been resolved in iOS 15, so you will be able to use cam2cam with audio if you upgrade your device to it.
Unfortunately, iOS 15.1 is experiencing connectivity issues. There is no fix currently available but we are working to resolve this. Apologies for the inconvenience.