touch id FAILED, doesn't let me enroll my fingers

Dear members,

my touch ID stopped to work.

I tried everything: erase the phone, restored, even full restore (MFU mode).

I cannot add a fingerprint, when I click "add a fingerprint" cames a message: FAILED.

Seens that it is desativected.

Anyone can help me?

I just bought this Iphone 5s gold, 64G in Honk Kong and as I live in Brazil they are refusing to replace the phone.

Best regards