Sometimes systems and drivers just get into confused states.
A restart will often clear up problems. If a restart or two doesn't fix the problem then move on to other troubleshooting steps.
Are you running the latest tablet drivers? The driver software will usually have some place where it says which version it it.
Try uninstalling, restarting the computer, and reinstalling the latest drivers.
Sometimes the drivers you have don't completely uninstall themselves. To completely uninstall the drivers see this guide: Uninstalling manufacturer tablet drivers.
Sometime newer drivers themselves introduce new problems that were not there before.
Try installing an older tablet driver to see if that fixes the problem.
Often the problems you experience might be due to a specific app so you should try other apps to see if they replicate the problem.
Krita
Clip Studio Paint
Photoshop
Microsoft OneNote
NOTES:
I recommend always testing with Krita because Krita is free and has configurable brushes that let you test our specific pen features such as pressure and tilt.
Try this: Testing with Windows PNP drawing tablet drivers
Often it can be a clue to what is going on.
If you are using a Mac, skip this section. It does not apply to you.
If you are using a Windows computer you need to be aware of a component called Windows Ink.
See these docs:
If you are having pressure problems check the pressure in the driver: Testing pressure in the tablet driver
In Windows, If the tablet driver detects pressure but the pressure is not working in an app, it often indicates that Windows Ink is configured consistently between the two.
It's important here to see if the where the pressure is working or not
Is it working in a specific app but working in others?
Or is it nor working in all apps?