Before you begin, please make sure the NVIDIA GeForce Now app is closed. You can close an app by pressing the keys "Command" AND "Q" at the same time on your Mac keyboard while within the app.
1) On your Mac keyboard, press the "SHIFT" + "Command" + "G" keys at the same time to bring up the Go To Folder window. In Go to the folder field, type the following text and then press the Go button:
/Applications/NVIDIA GeForce NOW.app/Contents/MacOS/GeForceNOWStreamer.app/Contents/Frameworks
2) Finder will open a window in the location above. Look for the cef folder and delete it.
3) Now relaunch the NVIDIA GeForce Now app.