It's not my network provider as it works fine in my Huawei P30 Pro phone. But it keeps failing on this one. Anyone else had this? Anyone know how to fix it?
Were you sure to turn off chat features on your previous phone before removing the SIM? Not sure it's still needed, but I thought at one point that was causing issues.
You can try force stopping Messages and clearing cache. Also, sometimes toggling WiFi off works for me when connecting RCS seems to get hung up.
RCS chat services can be glitchy and difficult to get working right sometimes. I missed some extremely important text messages that weren't coming through with RCS turned on, so I turned it off on my pixel, and am using the Samsung messages app on my Flip because I just don't trust RCS to get all my messages to me anymore
Hopefully down the road it'll get solid enough for me to trust it again