Digital Editions will not open my IPad.

My Ipad cannot read digital editions

I Buy digital books from the library ‘Libreria Rizzoli’ (rcsdigital.it).

But I can't download the ebooks on my  IPad . In particular, while using

BFRs BLUE FIRE READER, AdobeID stops me with the following message:

'''''''' add account ...This product has been downloaded with a different account or Adobe ID. You must

use the same Adobe ID. ... ''''''''

I am already registered on Adobe.  Can you help me?  Thanking you in advance