Do you did a big upgrade jump ? like Access 2003 to today ? as that bug existed back then; (.mdb to .accdb)
If such bug, you needed to open the database in an older Access, but newer than your old Access to do a first migration of the file, and then you can do the latest upgrade.
See the path;
- Open the Access 97 database in Access 2003.
- On the Tools menu, click Database Utilities, click Convert Database, and then click to Access 2002-2003 file format.
- Enter a name for the database, and then click Save.
- Exit Access 2003.
- Open the database in Access 2013 or later version of Access.
- On the File tab, click Save As, select Access Database (*.accdb), and then click Save As.
- In the Save Asdialog box, click Save.