This is the LBRY desktop app? Can you run sudo netstat -nav | grep -i listen and sudo ps aux | grep lbry in the terminal and post the output, if you’re still having this issue.
It usually just means it was already running in the background.
Try closing it from the system tray or task manager and try installing again.
If it still doesn’t working, back everything up, uninstall the app, restart the computer, then try again.
I see the post is 11 days old, so I guess you probably fixed it already?