I got a new tablet: veikk a30. One of the two buttons on the pen wouldn't work in krita even though it would work in all other programs. Changing the binding of the pen didn't change anything.
I fixed it by changing the tablet settings to "Windows 8+ pointer input" but this makes the pressure sensitivity stop working in krita. The tablet settings still shows pressure sensitivity working, but kritas tablet tester shows only a red line and no pressure.

I've tried reinstalling the drivers multiple times and restarting my computer, and I just installed the new version of krita.
If anyone could just help fix one of these two problems then I would be good to go since I only have one of them at a time.

If you switch Krita to Windows 8 Pointer API and the tablet tester in Krita doesn't show pressure, then your tablet only supports the Wintab protocol. And apparently it does it badly: most non-wacom tablets have the same problem with buttons though. You'll have to live with missing a button (or send this tablet back and get a Wacom).

Aw. Well thanks for the answer.