They are accessible, but not in the usual way: on the drop down option on the right for each file select “Send to” and then “Download a copy”.
I have no idea why they have been set up this way. It took me months to find out how to open them. To be fair, the instructions were sent to me, but I just assumed there was a file error. It never occurred to me that they wouldn’t be accessible in the normal way (ie by clicking on them).