Moodle 2.3.1 (Build: 20120706)
We've taken a complete copy of our flagship course (removing just the users), so we can upgrade the content. Content changes have been relatively minor (one additional Chapter plus text and heading changes).
The new course is now live (as v2), but students are reporting they cannot upload assignments (files). When we checked (using our test student login), the "Add Submission" button is missing from ALL the assignments. We've checked carefully the settings for a selection of the assignments, and they are identical to the (still working) v1 course. I have been unable to find out why the assignments are reporting "This assignment does not require you to submit anything online".
By chance, I noticed a spelling mistake in one assignment, corrected a single character, saved the assignment ... and the "Add Submission" button appeared!
I checked this with another assignment, this time not making any changes, just re-saving it - and the "Add Submission" button appeared.
We are using a very simple Moodle with nothing customised. This has to be a bug, doesn't it?