Unable to access "Edit in Desktop" on a shared document from an external company, how to fix?

Question

Hi! I have seen this issue flagged in other questions but from a few years ago - so I'm curious if this is still the case:

I am trying to collaborate with an external company on a shared powerpoint - while I have edit permissions and am able to make some edits via the web, I do not have the ability to edit within the desktop app. (not available in the pulldown menu as it is on other docs within my company).

Is this still a known issue - is there any additional permissions or ways I can do this? My ability to collaborate is really hindered by this!