If possible, try using a different keyboard to rule out any hardware issues with the current keyboard. If this solves the problem, you may need to take your device in for service.
You may try Fn + Backspace
Sometimes, a restart of the remote desktop connection can resolve temporary glitches. Disconnect from the remote session, and then try reconnecting.
Ensure that you are using the latest version of the remote desktop software.
You may also post here:
https://discussions.apple.com/community/business-and-education/remote-desktop