He changed his password back, you can start syncing.
i was syncing the rest of the trophies for that guy and suddenly he signed me out ...then i tried to sign in again and he signed me out another time (3 times this happenes ) after that i waited for like 10 mins then i tried to sign in again..and i found that he changed his password how am i supposed to continue my job like this...it took me 3 days to make him reach lvl 100