Personal workbook opens sometimes not others

The personal workbook opens for new files but not existing files.

Things I have tried:
If I try to record a macro on the personal workbook in an existing file I get two errors:
"Personal Macro Workbook in the startup folder must stay open for recording"
"Unable to record."

the personal workbook is not disabled in the trust center.
trusted documents and locations are not disabled

if I put in the location of the XLSTART folder in the "at startup, open all files in:" it works only until I close Excel: it then goes back to being blank.

I have literally no idea what to try next.

Please confirm that you do not have two versions of excel installed. My first thought is that one version opens via the short cut on the desktop/windows start menu, and the other version is associated with the excel file type so that when you double click a file that version is older/newer and doesn't have the personal workbook setup.