My prime stopped working

[Giancarlo]

Hello,
today my real Prime stopped working.
It's a 9cj7310### serial number
hw: c
sw: 2.1.14181 (2018 10 16)

Some Keys stopped responding. at the moment the Keys that are not working are:
HOME
APPS
5
6
TAN
LN
a b/c
*
-

I was able to do a back up, and after a couple of soft reset (ON+SYMB) i tried to do a hard reset clicking on 3 Keys and inserting the pin into the hole on the back of the calc. The result was a factory reset.

However it doesn't work. if you have an idea about what happened and if there is another test to do please suggest.

Thanks

Giancarlo