This might help someone else...
Using a Pixel 4a5G on Android vers 13, trying to add a card to Garmin Pay on a new Instinct 2 Solar Surf (which supports Garmin Pay).
Gets to the card select option (Visa, Mastercard etc) OK, but selecting a card option consistently ends up with msg "Setup Error: Sorry, something went wrong...."
All latest updates done on watch and phone and Connect app.
I've added a card years ago on my Vivoactiove 3, so know it should work.
Read an old post that someone had success with another watch model through an apple product, so tried through an Ipad.
Download and installed Connect, paired the Ipad to the watch, and the process to add a card went smoothly.
So, gotta assume there's an issue with the Android version of "Connect", as it can't even see the 2 cards I've successfuly added through the Apple version.