Welcome and be welcomed. Sun conure are not renowned for talking. They are too vain, being one of the most beautiful birds in the world, satisfied by your admiration of their gorgeous selves. Suns are very smart and can learn many tricks.
Not all parrots talk, just like not all humans sing or dance!
Now if he/she was talking before with you and has gone quiet for a few days, then that might be reason to be concerned. But you might have a shy little one or one who's just not interested in going out of his/her comfort zone.