@Mff73 was tryin that all, but failed.
I once said yes - I have one account. I never consciously assumed another. However, I must admit that I found an old phone where I have “lost” data and I see a different username there. How? I don’t know.
So now, yes, I have one phone that shows me data from several years, and which does not want to sync from the cloud on a new phone. I don’t see them on the app. The new phone only drops “new” data plus some prehistoric data from 2019. I don’t see the point in it, but I’d love to somehow import the data I see on my old phone. When I paired my watch with the old app, it took data from the watch without any problem. But when I go back to my new phone with my watch, all I see is this new thing.
Applications are updated. But there are actually two usernames, and worse, in the old app, I have a different email address that no longer exists.
Maybe the change in username happened when the email was changed?