Texting issues

my husbands phone will not let him individually text to my phone… he can receive messages from my line, but when he sends a message to me it replies back with “sorry, this service is temporarily unavailable, please try again later.” It looks as though it goes through as a text message (green bubble) but I do not receive it. texting and phone calls works to every single person in our contacts on both lines in and out, it is ONLY when he texts my line from his.

With the help of T-Mobile they said to delete my contact, re add it and text but now it won’t even let him send anything (the arrow won’t light up at all).

we have tried everything such as restarting, resetting, logging out of apple IDs, etc.

the other info we have is that when he tries to text my line sometimes (not everytime) when creating a text it says “me” as if he’s sending a message to himself. It is indeed my phone number but says “me” sometimes. Then other times it says “456” as my contact info.