Why is my Apple Bluetooth keyboard (a1314) not pairing with Mac mini (Late 2014)?

I am trying to pair my Bluetooth keyboard with a Mac Mini. The Bluetooth preference window shows the keyboard as "discoverable" however, when I try to pair, the keys don't seem to register when I try to type the pairing code. I tried it on my MacBook as well, and it doesn't work. However, on my girlfriend’s MacBook it does work. It seems to be an OS issue, as I am running macOS Monterey on the Mac mini and my MacBook, and she is running macOS Catalina. I don't really want to downgrade my OS. Are there any solutions that might work?