iMessage stopped working and won't re-activate on iPod Touch 6 gen

My daughter's iMessage and FaceTime suddenly stopped working and will not reactivate on her iPod Touch. I have tried network reset and made sure the date and time setting are correct. I have done a hard restart, airplane mode, wifi on and off, etc. I keep getting an activation error or a message that says the iMessage server can't be reached. We use this to communicate with her as she does not have a phone. Can anyone help or give me some advice?