Due google and avast say that the huion forums are not safe, I copy/paste this message with a problem like yours and the houion's answer:
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I just recently bought a GT-190 and it works amazingly… except with Paint Tool Sai. I don’t know if it’s the program or the tablet, but I’ve tried my legitimate version and an non-legitimate version my friend sent me to see if that would change anything. I was really hoping you might have some insight? It makes the pointer go to the left side of the screen and no longer respond to anything but horizontal input from the pen. Is there anything I can do? Thank you.
Posted on January 8, 2015
Thank you for your contact.
We understand that the monitor works fine except in Sai.
We wonder if the problem persists when you tried the legitimate version and the non-legitimate version of Sai.
Besides, would you mind trying the following driver to see if it helps?
https://www.dropbox.com/s/z14yt2psbtpuipw/PenDisplay20141031.exe?dl=0
Please make sure the previous driver and the other brand of driver are completely deleted from your mac and all the software and anti-virus programs are closed before you install this driver.
If the problem still persists, please contact service@huiontablet.com to ask for more help.
Thank you.