'No lens.' - Warning Message Appears
The adapter is designed to trigger a sensor inside the camera body itself so no setting needs to be changed. If the error message is coming up with one of our adapters attached, then it is possible that the adapter is not hitting that sensor the way that it should. Usually rotating the adapter slightly in the mount, or un-mounting and remounting the adapter clears the problem with no further action needed.
If that doesn't solve the problem, then the best course of action would be to swap out the adapter you have with a replacement.