Apple Watch Series 11 GPS + Cellular is unable to connect to cellular, no SIM

I have a new series 11 apple watch with cellular, but it's unable to connect to cellular. Cellular configuration item just say "No SIM" and "No Connection". Checking the IMEI confirms I should have cell capability.

I have the watch's IMEI added to my phone plan, but it's showing up as "unused" in my Watch App on my iPhone.

Can anyone help?

[Re-Titled by Moderator]

Original Title: series 11 watch+cellular unable to connect to cellular, no sim