Apple Watch won’t send non-iMessage texts.

I have an Apple Watch series 6, gps only version. When I send messages from the watch, iMessage recipients work fine. However, SMS messages will stall and eventually fail. I can send SMS messages directly from my phone with no problems, so it’s not a carrier issue. Both my phone and watch are up to date with updates, and I have turned them off, then the phone on, then the watch on multiple times. I have also verified that the Messages->Send as SMS setting is on.