I would try to de-compile before compacting. Make sure everyone is out of it completely if it's a shared database (make sure no 1kb files are locking it up too on other machines)

Run down the Troubleshooter.

Also right click the access icon on your desktop, properties, make sure it's not set to Read Only

One computer, One (Me) using.  Don't know what you mean when you say de-compile.  I'm just in progress on creating the app.
How would it get to read only?
thanks

It shoudln't get to read only, maybe some flunk accident caused it, it's worth checking at least.

Decompile is Compile

Not Read only. I can add,edit, delete, use VBA ect: Properties show its not read only

Access 365 Windows 11 on both laptop and desktop

What is the database showing under Options, General, New Database Sort Order.  I have changed mine to "General Legacy" with better results in compacting.

I don't understand why but after a all night-er I can repair and compact the database.  If I'm working on a db using a thumb drive I can't compact and repair.  ( I tried three different thumb drives).  If I'm working on a hard drive (internal or external) no problems compacting and repairing.  My only guess is that windows by default turns off caching on thumb drives to protect the drives from damage from a removal without doing a safe removal.
Wonder if someone would try it and let me know if they have the same experience.

Thanks for all your Suggestions

Sounds to me like another program is using the database. If its only when on the thumb drive, my guess is you have some security software "Holding" it, i.e. scanning but not letting it go. Try disabling AV software before plugging in the drive.

Ultimately, something is using your database file and you'll need to troubleshoot what it is - its unlikely to be an access issue.

"My only guess is that windows by default turns off caching on thumb drives to protect the drives from damage from a removal without doing a safe removal"
Yeah, this is an advanced possibility i would try but its worth investigating the simpler options first. Check your task manager to see if something is putting a strain on memory/cpu. If so, could be malware.

Yes, I recommend disabling your AV software and don't run the database from a flash drive. COPY it from the flash drive to your PC and then back again. I've actually had this on my list to make a TIP video about. Coming up soon.