Earlier quoted context omitted.
So is this like the Signal PIN which is required when installing on a new device? If you forget, the cryptography changes and old contacts are warned that signatures are rotated, right?
Yes, the purpose is the same but the UX is a bit different.
I have had all variations of clients ignoring requests, reporting requests only for the requesting client to ignore the response. Both ends quitting declaring that the other end cancelled, asking for the other end to input a code while the other end shows no interface for doing so.
It marked the end of me using Matrix as a platform. I'd go back to the old IRC channels if there were anyone still there.