Activity Friend Sharing is not working, stops working stats vanish

Recently, sharing my Fitness Activities via the Activities app with certain friends has been failing, and I can't figure out why. When I view their stats, their rings are just screened back with their percentage complete and their calories all represented by -- % and --/-- respectively.

For example, I had been sharing activities with a friend for the better part of a year when all of a sudden their stats just disappeared one day. And, I no longer got a notification when they completed a workout, so I could send them a cheeky message of encouragement. I checked my Activities app and lo and behold, screened back rings.

We've unshared our sharing and tried to re-share with each other numerous times. Each time, one of us will see each other's stats for a single day. The day we accept the invitation. Then the next day. Back to nothing. Neither of us has changed our accounts. Nor have we changed anything else with our Watches or our accounts. I even got a new watch, and I can still share it with my wife, and that's fine.

But yesterday, another friend's stats disappeared from my app. Screened back like my other friend. No more updates. This is getting strange. And we are at our wits' end because when we originally shared over a year ago, we simply invited the other person via email. Tapped accept in the Activities app and boom. It worked. Like you expect Apple software to work. But now? Now it's all kinds of broken, and we just don't know how or why.

Things we've tried:

-Restarting our phones

-Restarting our watches

-Restarting both our phones and watches

-Inviting each other, from both sides (her to me, me to her)

-I got a new watch, a new invite, and still no stats

-She got a new watch, a new invite, and still no stats

We are simply out of options. That's why I'm here. I never ask for help on the community forums. I usually can figure stuff out. But this. This is beyond my abilities.

I think that's it. Please Advise.