Welcome to TVPaint Community forums !

On an iMac Mic 2011 machine. OS X Yosemite V 10.10.5
3.4 Ghz Core I7
8 GB RAM
Dongle is not being seen. Sentinel drivers up to date on iMac. Is getting power from the USB port, as LED is illuminated.

Moving between a PC and the iMac. PC is running Windows 10 and no problems on the PC side.

Direction please?

Casey Herbert

What the hell is happening with Yosemite these last days

Neither the software nor the OS has changed (and both always worked perfectly well together).

So you confirm your drivers versions is 7.4.2 and TVPaint is 11.0.2 ?

How about this security update for Mavericks - El Capitan with Problem just released a week ago ?

• OS X El Capitan 10.11.1 and Security Update 2015-007
  　https://support.apple.com/en-us/HT201222
  
  À propos des correctifs de sécurité d’OS X El Capitan 10.11.1 et de la mise à jour de sécurité 2015-007
  　https://support.apple.com/fr-fr/HT205375

After the secrity update, I had to run Mavericks 10.9.5 Internet recovery mode and repair Wacom tablet driver (could not mount intuos 4 small) at once.