I use an old USB keyboard. After the last system update (Monterey 12.4) the number keys no longer work. Are these keys no longer supported?
Numeric Keyboard
Curious to know what you mean by "old" USB keyboard. I am using the Bondi blue keyboard from ye olden days of the iMacs and have had no issues thus far. You might try unplugging and replugging, restarting (all the normal jazz).
I found the problem. Yesterday when entering an accent, á, I inadvertently turned on Mouse Keys which reassigns the numeric keyboard.