Update (04/06/20): You can try installing the Play Store using this new method here.
Update: According to some reports, this method may no longer work on Huawei and Honor devices.
If you are having the “Device is not Play Protect certified” errors, here’s a way to fix the problem.
To give you a brief background, I myself have encountered this issue. It was my own curiosity that caused the error to appear on my phone in the first place, but I was able to fix it using this method.
Take note that this is what I did to fix my daily driver, a Huawei Mate 30 Pro, which started having the “Device is not Play Protect certified” error (it happened when I was testing other methods to install GMS when my phone already had it). I cannot guarantee that this will work with you or other affected devices, but there’s a big chance it will.
Warning: While this “how-to” is relatively easy to perform, it would involve processes like “sideloading” and such. If you are uncomfortable doing this, then I recommend that you do not to proceed.
Now that that’s out of the way, let’s get started.
First, check if your device is not certified (just in case the error message is not enough to convince you). To do this, go to the Play Store, tap the hamburger menu, go to Settings and scroll all the way down to About. You’ll see under Play Protect Certification if your device is not certified.
Get your Device ID. This is a 16-digit alphanumeric ID which you will need to certify your device with Google.
After installation, run the Device ID app then look for and copy the Google Service Framework (GSF).
Go to Google’s Device Registration page here and paste/type your Google Services Framework ID on the Android ID box and tap Register.
After registering, you may enter your Google credentials on the Play Store. And you might as well reboot your device for good measure.
It might take a few minutes for this to take effect, but this should register your device with Google and stop the ” Device is not Play Protect certified” error.
It bears repeating that I cannot guarantee that this will work with other devices experiencing the same error.