Just a note: there is not an ICCID until activation is complete. The activation process is where the the e-SIM is configured and the information is downloaded to your watch, this is when you will be able to find an ICCID.
Yes a common error is to confuse the ICCID for IMEI, hey I do it at least once a week. The ICCID is what in previous devices would have been called a nano-SIM, micro-SIM or SIM with the ICCID number printed on the SIM card.
So in an effort to see if this is hardware related or not, I installed 5.1 Beta 2.
One thing I noticed is the Watch App after the watch rebooted doesn’t show the IMEI but once I connect to the cell network it populated on the watch.....BUT does not on the Watch App on the iPhone. A subsequent reboot of the iPhone and relaunch of the app now shows it. (Just force quitting still shows UnKnown for IMEI)
I believe this is simply a bug in the App or Watchos5...
I've noticed the same. I tried to connect my Series 3 to LTE a few days ago via AT&T but cannot because there is no ICCID number. AT&T don't know what to do and Apple doesn't know what to do either. It's kinda sad. I might have to go to the Apple Store for a replacement.