Recording with iPhone Microphone in Non-Apple Apps

My new iPhone 12 will not record voice from any applications EXCEPT those made by Apple.

I thought the microphone might be broken. However, it will record for iMessages or the Voice Memos app.

But when I try to record voice using FB Messenger or Signal, no dice. It simply displays a play time of 0:00. However, I can re-record the message in Apple's Voice Memos and then send that to Messenger or Signal and it'll transmit.

Something is preventing non-Apple applications from using the Microphone. I can find no setting that will change this.

Has anyone else experienced this? Solution?