What does your Task look like?

Alex is asking the right first question: the exact Task Scheduler setup matters.

A few things I would check:

Make sure the task is launching the full path to MSACCESS.EXE, not just the database file.

Make sure the database path is in quotes.

Make sure the "Start in" folder is set to the folder where the compactor database lives. Access can behave differently when launched by Task Scheduler because the working folder may not be what you expect.

For testing, set the task to "Run only when user is logged on." Access is a desktop application, and running it in a hidden/non-interactive background session can sometimes hang if there is any prompt, trusted-location warning, missing reference, linked table issue, security prompt, etc.

I would also add a simple log table or text file to the compactor database so it records each step: startup, beginning compact, finished compact, and quitting. That will tell us exactly where it is getting stuck.

And finally, make sure the compactor database actually closes Access when it is finished, for example with DoCmd.Quit acQuitSaveNone.

Alex  Program: C:\Program Files\Microsoft Office\root\Office16\MSACCESS.EXE", argumentL C:\Users\Joseph\Documents\Compactor\My Database\Compactor.accdb"(compactor database).

Richard  When I set the "Start in" directory to the directory that the compactor dagabase is in, Ithe task fais with "invalid directory" I double checked - the directory I entered IS valid.

Double check your double quotes - the one you put in above is missing an opening "

Richard I verifiedf all strings are enclosed in quotes. I started over, directly browsing to MSACCESS.EXE, and copying full paths from File Explored to database and folder. II still get invalid directory  0x8007010B. I can run the contents of task successfully from cmd terminal.

Richard I was able to get the task to run successfully m,anually. I left the "Start in" field blank. However, I rebooted to see if it would run at startup, but it did not run. The status said it ran successfully, but the compacted database timestamp was unchanged from the manual run.

Alex is on the right track asking to see the exact task setup, because with Task Scheduler the little details matter a lot.

That 0x8007010B error is almost always related to the "Start in" path. Even if the folder exists, Task Scheduler is very picky about that field. Make sure it's just the folder path with no quotes at all, like:

C:\Users\Joseph\Documents\Compactor\My Database

If you put quotes in there, or if there's a typo or trailing slash, it can throw that exact error.

The other clue is that it says it ran successfully at startup but nothing actually happened. That usually means Access launched, but then got stuck waiting on something or didn't execute your code. Remember Access is a desktop app, so if it hits any kind of prompt (trusted location warning, missing reference, linked table issue, etc.), it can just sit there silently.

A couple things I would try:

Set the task to "Run only when user is logged on" while testing. Running in a non-interactive session is a common cause of this kind of behavior.

Double check the "Start in" path as above, no quotes, just the folder.

Consider adding a command-line switch to force something to run on startup, like using an AutoExec macro:

"C:\Program Files\Microsoft Office\root\Office16\MSACCESS.EXE" "C:\path\Compactor.accdb" /x AutoExec

That way you know your code is actually being triggered.

Add a simple log (even just writing to a text file) at the start and end of your compactor process so you can see if it's launching and where it might be stopping.

Also, if this is running at system startup, Windows can fire the task before your user profile (and things like Documents/OneDrive) are fully ready. Try adding a delay of 30-60 seconds to the task trigger, or switch it to run "At logon" instead of "At startup".

Since you said it works fine from the command prompt, that tells us the command itself is good. So at this point it's almost certainly Task Scheduler context, working directory, or timing.

Richard Great news! My task is now running suvvrddfilly. I started when I added the "/x AutoExec" option. It failed (I believe because there was no AitoExec macro(). It was if that failure woke it up. I then tried to run it again with no options and it ran successfully, I still have to leave the "Start in" field blank. I believe I have asystem problrm. Thanks for everyone's hel[.