Mary Cooch (personal account)

Well first of all, if you are an admin or teacher and switch your role to student you will NOT be able to upload - the assignment doesn't display as it does for a regular student (which is why I suggested you try with a genuine student account). If you are using MoodleCloud then I advise you to contact the support via the portal (the orange tab to the right of your screen when you are logged in as admin to your MoodleCloud site)

What browser are you using? (I notice it says drag and drop not supported) Are you as teacher or admin able to upload files in other places? I assume yes since there is a Word document uploaded to the assignment in your screenshot.

Hello RS. Before moving your question to the dedicated MoodleCloud forum, let's see if we can resolve the problem first:
Perhaps you can share some screenshots of what the student sees - are you for example definitely using a real student account inside a course? What browsers are you trying with? Did you change any permissions in the student account?

Hello. I.9 is very old and the problem is related to MySQL - you can see at least one tracker report here MDL-26284

The new feature in Moodle 3.11 allows you to rename the numbered topic section links to actual names - Section links block which might also help?