Delightful Downloads plugin: sudden drop in downloads!

Delightful Downloads plugin was working just fine until about a month ago. In fact downloads were flooding in nicely before that! Was even considering it now worthwhile adding priced eBooks to be downloaded on my site, considering the upsurge of interest in my art books!
Then all of a suddenly there were nil downloads been made on my website. So I tried downloading my own (FREE) eBooks, and it downloaded fine for me.
So why the sudden drop to nil downloads?
Has anyone else had this sudden nil result?
Is Delightful Downloads plugin no longer compatible with other plugins?
Any ideas how I can fix the problem?
My website is: adafagan.co.za