iTunes U - Share on Twitter not working ( error 3131)

Hello,

since a couple of days " Share on Twitter " is not working.

This happens everywhere: from any item, from any collection, from provider page.

The error reported is:

" We could not complete your request. There was an error in the iTunes Store. Please try again later. (3131)"

Share on Facebook is working fine.

Any idea ?

Regards,

Diego