Possibly because it's an XLSM file, which supports Macros. Macros have been used for all kinds of malware so Office apps ask if you want to enable them. There's a setting in Preference for letting them run without any safeguards if that's what you want.
If your spreadsheet doesn't use macros, then change the file ending to xlsx.
Other possibilities (from a quick google of "excel grant access") include sandboxing issues, usually to do with fonts in non-standard locations (if you use a font manager); or storing the file outside the user account (but that doesn't seem to be the case here). Make sure you're on the latest update, which may have fixes for bugs.
This is the dumbest security feature Microsoft has ever designed for Office 365, for macOS
I programmatically created hundreds of files, in a large number of folders.
Every time I attempt to read one of the file, Excel tells me to grant access to each one of them.
They are not corrupt, they are simple .txt files, containing data
Why would they do that!!!???
I found a solution.
It's because of a VERY poorly implemented design choice made by Microsoft, when they implemented Apple's Sandbox rules.
The work around is to rename the external using Apple's "temporary file", naming convention.
put, "~$" in front of any file name, that you want to read/import.
I can now read all my 684 text files, without having to grant Access. This solution works for me at least.
You’ve completed your recon, and found that your target is using MacOS… what next? With the increased popularity of MacOS in the enterprise, we are often finding that having phishing...