Troubleshooting & messages · Storage Studio itself
Why does it say Storage Studio is already running on this Mac?
Short answer: Only one copy runs at a time, so a second launch hands over to the one already running. Use the menu bar icon to reach it.
Only one copy of Storage Studio runs at a time — two would mean two sets of background jobs working on the same files. If you open it again while it's running, the new copy hands over to the existing one instead of starting.
Look for the icon in your menu bar. If you can't see it, the bar may be full; see the menu bar icon is missing.