Imessage keeps sign me out

Hi! I have macbook air 2013. Imessage and Facetime doesn't work. after i sign into Imessage it signs me out in about 5 secs. I tried restart and some other things, but it keeps doing it over and over. what should i do?

Facetime also has a problem. icloud id and password is definately correct, but i can't sign into it.