This finally worked for me!
“You are going to want to turn off RCS in your Messages settings, then turn on Airplane mode. After that, restart your phone. Then go back in, enable the RCS setting and THEN turn off Airplane mode and it should work.
This is assuming you have the bug where your contact’s messages come through as RCS, but yours still come through as SMS. And make sure they are the one who sent the most recent message, so the latest chat came through as RCS.
If you’re not already receiving as RCS, I don’t know if this will work. Apple pls fix”
***!!! This is the only thing that worked for me! I reset network settings, restarted, turned off iMessage, SMS and did everything else suggested in this thread and finally the airplane mode with RCS disabled restart worked for me. THANK YOU!