Error Message when attempting to open IntelliJ

Whenever I try to open IntelliJ and/or open a file using IntelliJ, I get sent this error message:

Cannot connect to already running IDE instance.
Exception: Process 426 is still running

I have already tried uninstalling and reinstalling IntelliJ and restarting my entire computer. I have a Mac so I checked the ActivityMonitor and was unable to see IntelliJ still running/if I needed to stop that Task. Any help would be appreciated!