With unlocked bootloader, you will not be able to use Android Pay on Google Pixel and Pixel XL smartphone. Unlocking the bootloader of Pixel/Pixel XL will trip the SafetyNet check (a security feature of Android) and Android Pay stops working. However, if you have enough reason to unlock the bootloader, but want to use Android Pay, then the new SafetyNet Patch can be useful. This patch bypasses the SafetyNet check, enabling to use Android Pay.
Essentially, SafetyNet Patch for Pixel/Pixel XL is stock kernel but added a patch to bypass the SafetyNet check. This kernel works only on Google Pixel/Pixel XL runs Android 7.1.2 Nougat (build NHG47K). It will not work on other builds. You can flash the new kernel via Fastboot, only if you want to bypass the SafetyNet check.
Bootloader is a reasonable security feature of Android, but it is also a problem for anyone who wants development on his or her phone. For security reasons, Android phones are comes with locked bootloader, so if you unlocked the bootloader, some features will not work, such as Android Pay.
Note: Keep in mind that this patch will not bypass the SafetyNet check, if it is tripped by rooting the phone. Also, it works only on Pixel/Pixel XL runs Android 7.1.2 Nougat build NHG47K.
If you unlocked your Pixel/Pixel XL bootloader, and want to bypass the SafetyNet check, then you can flash the new kernel via fastboot.
How to Use Android Pay on Bootloader Unlocked Google Pixel/Pixel XL
Disclaimer: The guide is for tech-savvy users only. It must be done entirely at your own risk. We cannot take responsibility for anything that goes wrong.
1. Make a backup of your current ROM or download factory images from Google for your Pixel/Pixel XL, just in case.
2. Download Pixel/Pixel XL Kernel with SafetyNet Patch from here / source
3. Unzip the downloaded zip file and save the unzipped file inside the ADB/Platform tools folder.
4. Open a command window inside the ADB/Platform tools folder and issue the below command:
fastboot flash kernel <filename>
For more details and discussion about the Pixel/Pixel XL Kernel with SafetyNet Patch, go here.