You may encounter the "HuionTablet needs access to accessibility" pop-up message after installing the driver, even after it is ticked.
The root cause is due to the improper driver uninstallation before reinstalling it.
Please refer to the following steps:
1. Go to HuionTablet > Preferences
2. Click on "Uninstall" to uninstall the current driver
3. Go to "Security & Privacy"
① Click "Accessibility"
② Choose "HuionTablet"
③ Click "-" to delete it
4. Reinstall the driver according to this article: How to Install Huion Driver on MacOS.