Apple Watch ultra not showing sunrise/sunset time on display

Force Restart Your Watch:

Press and hold BOTH the digital crown AND elongated power buttons at the SAME TIME. Keep holding them both until the screen goes dark and keep holding them until you see the Apple Logo, then let go. Sign back in when prompted and see if the issue is resolved. It will take a few seconds after you sign back in for all complications to update.

Yep, you don't have a VPN profile. Do what LD150 suggested and reboot your home router (just unplug it for a minute, then plug it back in). Once it comes back up and your reconnected, hopefully you'll have the complication function as expected whether on Wifi or Cellular.

Maybe the Series 7 showed it on OS8 but did the Ultra ever show it?

There was a change when OS9 came in that reduced the information on that complication and has led to some complaints.

https://apple.com/feedback

Your watch gets such data from the iPhone Weather App. The official one from Apple. Have you configured the weather app on your iPhone to your local city?

The app you should have on your iPhone and Apple Watch is this:

VirtualEnergy7 wrote:

Agree, my buddy has the same watch (the ultra) and it displays in his.. for me I have to actually click on the icon for me to see what the times are .. it used to work on my apple series 7 watch

New information is always welcome.

You're welcome. I'm sure they'll get it sorted for you. Before you do however, I don't recall either LD or myself asking if your watch is updated to WatchOS 9.2 (the most current WatchOS version)? If no, update your watch. The Force Restart your watch after the update and see is this resolves.

That's great. Do you by chance use a VPN on your iPhone? If yes, DELETE it. VPN on iPhone is simply not necessary and can cause way more issues than it could possibly solve. We know your watch is working correctly on cellular. Maybe the connection from your iPhone when on Wifi is an issue.

Oh, you beat me to it lg1! I agree, particularly if the problem returns when wi-Fi is reconnected

I would also reset the router to factory settings and reset network settings on the iphone for good measure,

If that fails to help I would go the step further, find that little Reset hole and stick a paperclip or SIM tool in for 10 seconds to reset that router to factory settings.

Some routers have a software menu reset but most have the little hole.