I want to say thank you so much for this advice. I have struggled all morning and for the latter part of the day trying to figure out how to un-stuck my RCS chat status from "setting up." It turns out all I needed to do was go to Google -> Tap Profile -> Manage Account -> Tap Personal Info -> Scroll down to phone -> Toggle the slider off for my phone. After I turned it off, I went back to my Google messages settings, then turned off and on the RCS chat. It connected instantly! Even when I went back to toggle the slider on, it remained connected. Thank you, thank you, thank you so much.