Messenger app without Facebook

My granddaughter and I are not able to send messages back and forth thru messenger app. She has facebook, I don't. We used to be able to , then I had to redo my messenger on a new phone, now when I try to add her to messenger, it says "something went wrong try again" and she gets the same error when trying to add me to hers. I have also gotten one that said "unavailable right now"

I only use wifi on this phone, it is not an active phone. but either was the old phone I was using until it died.

thanks
trina