Ever since my wife got her new phone I cannot text her. When I text, mine shows up as green, and it never gets delivered to her phone. All the other people she texts with seem to have not problem. I have gone round and round the settings and send as SMS and such. While it seems like a problem with my phone the fact that it began after she got a new phone makes me suspicious.
What happens if you text to her Apple ID (not the phone number)?
Are you logged into iCloud?
Did she change from an iPhone to a non-Apple phone?
So I just looked at her phone. I was blocked. Allegedly not on purpose, but at least the mystery is solved.