TL;DR – Samsung Pay seems to have stopped working on smartwatches if you don’t have a Galaxy phone. Seems to be a bug.
Samsung Pay on Smartwatches appears to have broken the tap to pay feature for many when paired with non-Samsung phones. The error you’ll get back is that the account is invalid, although you can log in with no issues.
The issue appears only on non-Samsung devices, where the Samsung Pay app is not a system app.
I highly suspect bug as opposed to devious corporate strategy to sell more phones, although with one person from Samsung support saying that’s the case the internet jumped on it. You’d think they’d just announce in the Samsung Pay app that it was discontinuing as opposed to pushing an update that broke it and gave a vague error message, but you know…[9to5Google]