Wireshark or one associated with it is already running

Alternatively you can also use the Windows cmd command

tasklist | findstr -i "cap"

And then check for any of the wireshark related component, something like usbcap, dumpcap and if you find one, use the below command to kill it.

taskkill -f /PID xxxx

Where xxxx is the process ID of the output of the first command.

It's hard to say without knowing which OS you're running, but generally you should open up your task manager and see if there are any Wireshark or Tshark or Dumpcap processes still running that would cause this. Optionally also try rebooting...