I have to keep re-registering my device

Hi, I have used Garmin for many gears, I had a Fenix 3 for years and upgraded to a Fenix 6 pro solar in 2022, which has been great.  For over a year I had no problems, but out of the blue in June 2024 I noticed it wasn't connected to my phone.  The device had disappeared from my account.  Not a big issue, 10 mins later I had added it again and received an email thanking me for registering my device.  I assumed this was a one off, but in July it happened again, then beginning of August and then yesterday (14th August).  If I plug the watch in on my PC Garmin Express sees it just fine, but I have to sync it, and another email thanking me for registering it.  And I still have to go through connecting it to my phone.

What's odd is my Fenix 3 was stills showing in my account even thought that's not been connected for years (I have manually removed that now).  It would be a minor frustration if it only happening once a year, but this is now happening every 2 weeks, and I have to go through receiving new records on my longest ride, reading through tips that I have seen before etc etc.

Can anyone help please?!