Hi facepainter,
Does the onscreen keyboard work for numbers? If so, check your external keyboard settings allows full access.
To check, navigate to "Settings > Accessibility > Keyboards, tap Full Keyboard Access, then turn on Full Keyboard Access."
You can also find the steps here: Adjust the onscreen and external keyboard settings on iPad
Additionally, you can test unpairing and pairing the keyboard again. Set up and use Bluetooth accessories on iPad
"Unpair a Bluetooth device Go to Settings > Bluetooth, tap the information button
next to the name of the device, then tap Forget This Device. If you don’t see the Devices list, make sure Bluetooth is on."
If the issue continues and this is a third-party keyboard, reach out to the manufacturer to further assist.
Contact a third-party vendor
Best!