I was losing my mind with this issue. A few weeks ago I suddenly had this happen with my Watch 8. My fitness friends went missing on my watch (but they were there on my phone). I no longer got their activity notifications and on my friends’ end, they also stopped getting notifications of my activities and my rings for them all had zeros. I FINALLY figured out that in the Watch App on my iPhone, it signed me out of my Apple ID. (Apparently having the watch paired with the phone isn’t enough.) Try going into the General settings of the Watch App and then Apple ID. When I went into it, it had a message asking me to sign in. Once I did that suddenly all my fitness friends appeared again in my watch and we started getting notifications with each other again. My friends also accurately see my ring status. So if you have zeros from your friends I would also have them try this. The problem could well be on both ends.