Why aren’t my contact names showing up on my Apple Watch series 3 anymore?

So a couple of things... Is your iPhone on 11.4.1? Which should be the newest iOS 11 version out.

And have you tried to to the 'Reset Sync Data' option in the Apple Watch App on your iPhone?

(go to Watch App - General - Reset - Reset Sync Data). Often that Reset Sync Data option will correct it. You will not get any type of confirmation its doing anything as it happens in the background. But try it and check your Watch contacts after a few minutes to see if they are sync'd properly.

If you have the iOS 12 Public Beta on your iPhone you will experience this issue. Many others here have reported it as well.

There seems to be a issue between WatchOS 4.3.2 and iOS 12 Beta 3 syncing contact info.

Some others have reported that Beta 4 has corrected it but the Developers version is the only one out currently. Public Beta 4 possibly will be released this week if they follow their past schedules.

WatchOS 5? I am on WatchOS 5 dev 2 and it is an issue. I am upgrading to dev 3 RN.

Make sure the Bluetooth on the iPhone and Apple Watch are on and synced. and you are all set!!! ;)