I have yet to get my Active 2 to work with Samsung Pay. The credit cards are all properly on the corresponding phone (Note 20 Ultra) and I see the cards to select them. However, when I place the watch near the payment NFC reader, it never works. Once in a while I'll get a "Payment Cancelled" error on the terminal. I end up having to use my phone for Samsung Pay which works just fine.
I've reset the watch and reset Samsung Pay as well, reregistering the cards but no go.