QuickBooks Unable to Open Company File

Hello TechyV experts!
I havve downloaded a QuickBooks Company File Diagnostic Tool software to deal with this error. I ran the diagnostic tool and it said no problem detected in the company file (that I was previously trying to open).
But when I tried to open the file again, the same error came up. I’m confused at what’s going on here.
If the tool can’t detect any problem, what is this error coming up for?
Hoping for your ideas and suggestions regarding this error.
Thanks!

Warning
QuickBooks is unable to open this company file.
It may have been opened by another user. You should ask that user to switch to multi-user
Mode so you can both use the company file at the same time.
The file could also be located in a read-only network folder. If it is, ask your system
Administrator to make the file accessible (-6073,-816).
OK
