Ok, got an official answer from Cadillac:
As it stands, the only way to reset the CUE system on XT5 and CT6 is to do a soft reset by turning off the vehicle, opening the driver’s door and waiting for the accessory power to drain. Once the lights and screens turn off, the soft reset has been completed.
Note that there isn’t a hard reset for the CUE system specifically.
If that solves the issues you’re having, great. If not, you can try restoring the system from within the CUE settings.
PS: I should have asked first — what kinds of issues are you running into?
