Use tweezers to flip up the small, hinged locking flap in order to unlock the ZIF connector securing the Circle Pad ribbon.

The cable folds over itself and enters the ZIF connector from the left side, but the connector's locking flap flips up from the right side. A common error here is to try pulling up on the same side as the cable is on, when that could break the connector.

Slide the ribbon out of the ZIF connector.

It may be easier to unscrew and remove the Circle Pad first, then try disconnecting the cable. Similarly, when reinstalling the Circle Pad, you can reconnect the cable first and then put the unit back into place.