Can’t see Activity sharing notifications. Not receiving invites

This is an absolute nightmare. My friend and I have sent over a dozen invites to each other but neither of us are seeing the invite. Both of us have the same watch iOS 6.1.1 and phone iOS 13.3. I’ve reset phone as new, signed out of iCloud about 50 times spent the whole of a Saturday and still can’t see each other’s notifications for the record there’s four of us in total.

And two of us managed to share at first but it was incredibly buggy - one wouldn’t show the others progress.

I’m seriously considering returning the watch and going back to Fitbit. Seriously you would think this would be simple on apple and a nightmare with Fitbit. But the fact that Apple have had about 4 years to sort this and it’s still as buggy as ever - it’s a joke.