Your device requires a Thread border router

I am developing a Matter device using the nRF 5340 DK. I had this working and for some reason it isn't anymore. I am using the unmodified light_bulb example from the Nordic SDK. I built and ran it on my 5340 DK.

I have a Smartthings hub that is already connected and working with my Android phone and the Smartthings mobile app.

I get a notification on the phone that there is a new device. I assume that is because it is advertising.

I have the QR code in a browser window from the URL in the debug output.

When I scan it it takes a few seconds to connect and then gives an error:

"Your device requires a Thread border router"

I don't understand. The Smartthings hub is a thread border router and it all configured and ready.

Please help.