Signup overwrite always last inserted record

Hi,

I need help when adding new records.

When I add a new record with Signup, the first time it is ok, but when I try to add a second/third/etc.. record, it goes to overwrite the last one inserted in the session.

If I clear the browser cache, it again create the first entry (different Private Id) but again it will not add new entry (same Private id).

I changed the relative option on admin panel for the Signup “to create new record with the submission” , on the Testo field (unique textfield) but nothing change.

Please help me to allow everyone (even not logged user) to insert data without update old entrys.

Thanks

Antonio

The page I need help with: [log in to see the link]