Garage Band won't pick up my UR22mk2 as an input device

Steinberg Hardware UR Series
2

What OS are you running?

Youll want to check here and make sure anything UR22 is enabled where you see it in those tabs

Select System Preferences… from the Apple menu.
Open the Security & Privacy panel.
Select the Privacy tab.

https://helpcenter.steinberg.de/hc/en-us/articles/115001525990-Yamaha-Steinberg-USB-driver-installation-on-macOS-High-Sierra-10-13-