I'm trying to move some courses from an old Moodle 2.7 site to a 3.5.4 site. I have exported one of the courses, download the .mbz file from the old server, then uploaded it to the new server. The max upload size setting on that server is set to unlimited & I've tried downloading the file again from the new server and unzipping it & file is readable and has the moodle_backup.xml file in the root.
However, when I try to restore the course (using Site administration/Courses/Restore course), I always get the message "The selected file is not a valid Moodle backup file and can't be restored".
I tried with another course but get the same result.
I don't have ssh access to the server this moodle runs on, only admin rights in Moodle itself, when I go to Reports and look at all activity for today, it has nothing logged about the attemped restores.
Any ideas about why it dosn't seem to accept my backups as valid files?