Hi p1r473,

Your error could likely be due to a recent Windows update.  After windows rolled out the CPU bugfix a couple weeks ago, one of my GPUs stopped working again.  If you roll back this windows update, it may work.  (Uninstalling the windows update got me all 6 GPUs again).  Note you should be careful what you use the machine for if you remove the windows update patch.

Good luck,
Russell