iPod 5 iMessage won't activate

Hi there

I have an iPod 5, and for some odd reason one day, my messages weren't sending. So I turned off iMessage then turned it back on, and it asked for me to sign in. I did and the password and username were correct but it said "Signing in" for a while. Then it gave me a pop up saying "FaceTime activation failed" I've been trying for three days and have done everything I've heard to do including changed date and time, try again and again, reset ipod nothing is working. What do I do?