also check out bebop's answer here:
its a longer version with some extras. For the QUICK AND DIRTY VERSION:
Found this, it fixed my issue which sounded similar to yours.
This is the code for HUION New 1060 for example: HID 256c:006e Pad
xinput # get the IDs for all relevant pieces of my tablet.
blah blah: HID 256c:006e Pad id=17
there might/should be two devices, Pad and Pen. Then do:
xrandr # get the names of my displays
look for the ones showing 'connected' like HDMI-A-0 connected
and maybe DisplayPort-2 connected
Then you tell xinput to stick the id's to the screen you want Krita or Photoshop on, such as if you were using a HDMI port to main screen:
xinput map-to-output 13 HDMI-A-0
xinput map-to-output 14 HDMI-A-0
that was mine.
it resets after a reboot. thanks to that user timotimo!