You may need the latest Universal SafetyNet Fix from here:
Google SafetyNet attestation workarounds for Magisk - GitHub - kdrag0n/safetynet-fix: Google SafetyNet attestation workarounds for Magisk
github.com
To use this new version, you will need Riru, from here (installed first, then reboot, the try USNF above):
Inject into zygote process. Contribute to RikkaApps/Riru development by creating an account on GitHub.
github.com
Do a clear of google play store/services and google pay afterwards, and if still no luck with google pay, remove card and readd...
* Be aware that you should not use the very latest Magisk Alpha (706a4922) with Riru as it has known issues at the moment.