This is likely due to the database splitter having problem processing one of the tables.  Check which tables were successfully split.  The splitter likely stopped at problematic the table, so one of the tables that weren't split is the culprit.  Try manually splitting those instead.  I always manually split tables and never use the splitter tool, which may have bugs.

thanks Kevin, would you talk a little bit more about how to manual split
thanks

Watch this first:  Split Your Database

Actually not difficult at all.  Back up your current db.
Make two copies of it.  Name the first one "yourname"FE.accdb (FE = Front End)
Name the second one yournameBE.accdb (BE = Back End)
The name isn't important just so you know which is which.

Open the Back End copy and delete everything except the tables.  Save and Close it.
Open the Front End.  Delete all of the tables.
Now go to External Data --> New Data Source --> From Data Base -->  Access
In the dialog that comes up choose Link to the data source by creating linked table.
In the top line browse to the location of your BE copy.
In the next form that comes up select all of your tables and Click OK

thanks Scott, I did it
But the front end cannot be save as .accde  file

You probably have a syntax error in your vba code. Debug compile.

Thanks Richard
It works

Yeah, this comes up a lot. It's one of those error messages that could be a little clearer. They could easily add "try compiling your VBA" to that error message, but it's one of those things that unless you've experienced it, you don't know to look for it. Next time you get an error message, Google the exact text. In this particular case, you would have found my compile video; I just checked, and it's the number one video for that search.

And if you do search for an error message and my video doesn't show up, then let me know and I'll make one. LOL, that's my goal... To be the number one video for anything Access related.

with the help of your videos and your team and chatGPT
I solve 90% of my questions