I got a new 15. Put all the data over from my SE 2020 that was connected to my Apple Watch.

I disconnected the watch from the SE. it says it doesn’t have a Watch connected and asks if I want to connect one.

I now try to connect it to my new iPhone 15, but that one keeps on saying it was unable to connect. What step am I missing?

Edit: tried to reconnect it to my old SE, but that one also failed to make a connection now.