I have always found this to be the case, as the beta version is not the official version so its not rooted. When the official version does go live and your phone receives it you will be able to use Google pay again
In the mean time I'm using Samsung Pay for contactless purchases. Additionally, Samsung Pay has a big advantage over Google Pay as it does not require NFC activation manually before purchase. NFC is toggled off/on/off during the transaction period with Samsung Pay. Neat.