Well, it was nice while it lasted. A few months ago prolific Android developer Chainfire introduced a method of rooting Android devices without modifying the /System partition. It had the added and extremely welcome benefit of getting around SafetyNet detection for applications that were intentionally disabled on rooted phones, like Android Pay. But it looks like Google has caught on: starting this weekend (as reported on the /r/Android subreddit ), Android Pay and other SafetyNet apps no longer work with the roundabout root method. Bummer.
Google's system uses a server-side update, so at the moment there's no way to get around the check even with older versions of Android Pay, Google Play Services, et cetera. If you're a regular Android Pay user with Systemless Root, you might not see the effect immediately, since the app doesn't actively request a token until you add a card or make a purchase. But the party's over, so turn out the lights and give your requests to the fat lady.
At this point you can still unroot your device (or simply flash a stock image) to regain functionality in Android Pay and other SafetyNet apps. Chainfire and others will probably take a shot at another work-around solution, but there's no way to know how successful they'll be right now.