Failed to connect to database. Not a valid file name (ArcMap, personal geodatabase)

Windows 10, ArcMap 10.8, local parent directory, personal geodatabase

I tried solutions suggested for this problem but they don’t work. I have several similar ArcMap projects for different regions. In some projects layers are not accessible and when I try to change the data source an error pops up: "Failed to connect to database. An underlying database error occurred. Not a valid file name".

I tried changing the database file name, tried to change the directory of the file, tried to run AccessDatabaseEngine but nothing works. Some solutions suggested deleting the file lock but I don’t have it in the file directory. When I open the DB in Access I can see the attributes, it doesn’t suggest me to fix the DB (I don’t have licensed Office but other ArcMap projects still work).

Those projects that DO work are dated this year and those that DON’T are dated last year so I thought there could be a compatibility problem. Unfortunately, because I have not created those projects I don’t know which ArcGIS version was used.

How can I fix this issue?