Can't open Mac - Another copy of error

I cannot open on my iMac 2023 (M3). I get this error “Another copy of Setup is already running on this computer. Please close it and try again.”

I’ve redownloaded many times and did the Blizzard recommendations:

“1. Log in to the other user account, sign out, exit the desktop app, and try again.
2. [Delete the Tools folder]
3. Restart your computer to resolve problems caused by programs and services running in the background.”

All to no avail. Any suggestions? Please and thank you!