Can you clarify a bit, please?
What used to recognize the iPad?
What software are you running on the iPad?
Digital editions won't recognize ipad. i have an ipad 3 with the last software
Which software are you using on the iPad to read eBooks?
As far as I am aware, ADE never had support for iPad.
You need to run something like Bluefire on iPad and sideload the books from PC using iTunes, DropBox, email or similar.
However, that does not tally with your initial comment It used to recognize iPad but no longer
So, please clarify.