What is WRONG with your software?

Works fine for me, probably it is your setup (your phone?)

You’re right of course. I left the “have Garmin Connect sync just not work the first time, except on Saturday when it was fine, so that you have to kill the app and restart it” option ticked on iOS.

It used to work fine for me too and I would very much have liked that state of affairs to continue.

Why is it even using Connect if I have wifi enabled?

Just to add that this problem went away by itself one day. As mysteriously as it appeared.

Used to be solid and reliable. Very flaky recently.

Sync with Gamin Connect after a ride has always been flakey, but it seems to have improved incrementally in recent years. Still not perfect though (and my local network and WifI perform just fine for everything else). Every once in a while I still have to restart my Garmin and or Garmin Connect (iOS) to get things flowing.

The problem is not the device but the Connect app on the phone.  The app is super flaky.  To solve this problem for good I don't use my phone for sync.  I disable phone connection and enable WiFi.  When I'm traveling where WiFi isn't available, I create a WiFi hotspot via my phone, and sync via the hotspot WiFi.  With WiFi it works 100% of the time.