Final update
As today, Italian CAA not rejected, but suspended my skill test application because they require UK CAA approval of my UK PPL exam results.
Course completion certificate (ATO Signed),
Exam results paper (ATO Signed),
Proof of payment (to ground school),
and Ground School ATO Certificate
are not enough Italian CAA to confirm my exam results integrity.
Can anyone tell me how to get my exam results document approved by UK CAA?