Basically the latest drivers won't see a monitor if it's been driven by an eGPU in MacOS Mojave.
6.3.30-2 is the latest driver that that works with eGPUs.
Please Wacom.
Wacom Customer Support page: https://support.wacom.com/
Wacom Product Resources - Drivers, Manuals, Warranty Information & Others
Pen not working after Mac OSX update June 2019:
http://forum.wacom.eu/viewtopic.php?f=11&t=4011
Why is the cursor on Windows a white dot or crosshairs?
http://forum.wacom.eu/viewtopic.php?f=11&t=4013#p8912
Mac OS 10.15 Catalina Beta:
https://www.wacom.com/en-us/support?guideId=015-916
Product Registration:
Please register our products on https://www.wacom.com/register
How do I register my Wacom device?
Drawing software:
If you wondering which software to choose, check the trial versions below:
Wacom Product Resources - Drivers, Manuals, Warranty Information & Others
Pen not working after Mac OSX update June 2019:
http://forum.wacom.eu/viewtopic.php?f=11&t=4011
Why is the cursor on Windows a white dot or crosshairs?
http://forum.wacom.eu/viewtopic.php?f=11&t=4013#p8912
Mac OS 10.15 Catalina Beta:
https://www.wacom.com/en-us/support?guideId=015-916
Product Registration:
Please register our products on https://www.wacom.com/register
How do I register my Wacom device?
Drawing software:
If you wondering which software to choose, check the trial versions below: