I cannot send SMS/RCS message from iPads

I have two WiFi M3 iPad Pros and an iPhone 17 Pro.

This afternoon, I noticed that I could not send SMS or RCS messages using either iPad. When I try to, the name under the recipient icon in the message window has a green bar beneath it and after a few minutes, I get a Message Failed to Send error.

I have made sure that I have Text Message Forwarding turned on for these devices on the iPhone. I am able to send SMS and RCS messages from my iPhone, from an MBP and an MBA. It’s only the two iPads that are affected.

Apple messages are unaffected. I can send Apple messages from any device.

I have tried rebooting both the iPad and the iPhone multiple times and it has made no difference. I also tried turning off and on iMessage on both the phone and the iPads and that too made no difference.

I have run out of ideas. Are there any suggestions here on how I might get this working again?

This is what the icon I’m referring to above looks like:

[Edited by Moderator]