Hi!
The project currently doesn’t contain a complete simulation setup, so it’s difficult to know for sure what the settings were. However, from your description, it feels like you were defining boundary conditions to contact faces (which is forbidden, i.e. this page).
If you’re looking to set internal fans for CHT, currently the way to go are momentum sources. You can remove the internal fan volumes from your CAD model and set momentum sources instead.
Cheers