Problem Solved!!
It was because the Title was too long!!!!
The title line on our databases include the name and address of a member who is running a collection (we are a charity group) and her address was quite long. ?In desperation, as I had tried everything else, I trimmed it down and once that was done I was able to download the file.
Sorry for taking up your time. ?I very much appreciate the ability to ask fellow group leaders for help.
Have a lovely day,
Pamela