I'm on Google Pixel XL Unlocked and Rooted with Magisk 18.1 and on March 2019 security update. Thought I'd save others some possible frustration and embarrassment like I suffered this morning at the grocery store (with my wallet in the car)....it appears that the most recent updates to Google Play Services (I am on 15.0.0, but others are saying the issue occurs on 14.8.49 and higher)....circumvent MagiskHide and prevent Google Pay from working for payment in stores. Really strange in that SafetyNet still appears to pass. Hopefully an update to Magisk/MagiskHide will be incoming soon. You can track the progress and others' experiences at this thread within the Magisk forums....also there is a workaround posted within that thread that many have reported success with...it involves downgrading Google Play services....
https://forum.xda-developers.com/apps/magisk/discussion-google-pay-magisk-discussion-t3906703
Good luck!
S
https://forum.xda-developers.com/apps/magisk/discussion-google-pay-magisk-discussion-t3906703
Good luck!
S