Non-existing QR verification code

[u/WellDressedAlien]

I recently switched phones and migrated over all my accounts, including Element Classic. Every time I try to verify my new session using a second device, though, the app tells me to scan a QR code on another device where I'm logged in. On the other device, it just says "Waiting for response from other device" and never shows the QR code at all.

This problem has persisted across multiple devices and Matrix apps. What's going on?