We found some problem with content in your excel - .xlsm getting error while .xlsx doesn't

Hi,

Whenever I open an excel file with the .xlsm extension, I get the error We found a problem with some content. It is tricky since that particular file can’t be opened later in production.

I tried almost everything to fix this problem: Killed all excel instances, tried workbook activities, etc. Nothing worked.

What confuses me is that I have a .xlsx file that contains macros as well, but I rarely get this type of error.
What could be the reason for that?