Symlink used - "Unable to start. The Sims 4 is already running" Message

 I've games via external usb for about 2 years now on a 128GB usb. I bought a new usb with 256GB and I recently moved my game data and game onto it. However I keep getting the "unable to start" message.

The USB is plugged in correctly. EA and TS4 have full access to my document folder and iCloud is not involved. I'm not really sure what to do here.

Any help welcome.