Cannot open Musescore file

For the last couple of weeks I have been experiencing difficulties in opening MuseScore on my laptop.

To begin with, when a student sent me a piece in mscz format, I had no difficulty opening it, having downloaded MuseScore onto my laptop.

A week later, I received another file in mscz format from the same student, but I was unable to open it.

I received an on screen message that the file is not in the correct format.

I went back to the earlier file that I had previously accessed, but I received the same message: file not in the correct format.

I deduce from this that the problem lies at my end.

I have a MacBook Pro that uses macOS Mojave Version 10.14.6.

I deleted my current version of MuseScore (3.5.2) and updated it to 3.6.1.

I tried to open the file a second time, but I received the same message: the file is not in the correct format.

Any suggestions?