No problems with Wacom Intuos 5 Touch and the latest PixInsight release on my iMac Pro running Mojave OS.
You don’t say if you are running PixInsight on Windows, Mac or Linux OS, or which PixInsight version you using, but possibly a system update on any of these platforms may have caused the issue.
Check that either PixInsight or ‘All ’ applications, is showing in the controlled applications list of the Wacom driver and if not listed add PixInsight to the list, this is accessible via the Wacom icon in the Mac System Preferences control panel. As a Mac user only I can’t advise where you will find this on other OS’s, sorry.
If no obvious user configuration issues then reinstall the Wacom Intuos 5 driver with the latest available from Wacom’s web site, driver version 6.3.32-4 is the current release for both Windows and Mac:
https://www.wacom.com/en/support/product-support/driversLinux Kernel driver, X-driver and libwacom for Intuos tablets are available at the Linux Wacom Project on Github:
https://linuxwacom.github.ioIf still not working then reinstall PixInsight, though this sounds more like a driver problem than a PixInsight issue.