Same with me. It's frustrating because I cannot follow the amount of my monthly steps on my Watch4. I think it's a bug and I hope it would be fixed soon.
I found a small work-around. Make a personal challenge, when you add this one the Global are visible.
Note: Don't delete the personal challenge when done, then also the Global disappears
Lets hope for a quick solution in a new release
I have to same issue but I not sure how you guys find a work around, on my watch there is one button - 'add' which just give a 'there are no challenges' message. Despite having made my own challenge with invited people and joining the global challenge... hot fix anything? It's an expensive watch for small issues to last so long.
Add a challenge (invite a friend), as soon as she/he accepts you can view your data from "Together". When accept you can add this from your watch (then this button works)
Note: Stupid that this feature (we had before) is still not implemented again