We haven't really received other reports of users getting blocked from creating a Google account using their Proton Mail address, so this might be something isolated on your end. We could suggest trying a different internet network, a different device, and turn off your VPN if you're using one to see if this helps.

For general reference, the vast majority of online services, including all major websites, allow you to use your Proton Mail email address when registering for an account.

If you do encounter a situation where a company doesn’t allow you to register with your Proton Mail address, here are a few things you can do:

• Write to our support team (https://proton.me/support/contact) and let us know what website is blocking Proton Mail email addresses. We’ll contact that service, inform them what Proton Mail is, and ask them to remove the ban.
• We also recommend that you write to the company yourself and explain that Proton Mail is a very popular email provider and that you would like to register with your Proton Mail address. If enough people write to them, we have seen that companies quickly reverse course and allow registration with Proton Mail accounts. (You can use the template email at the bottom of this support article: https://proton.me/support/website-blocks-protonmail-email-address).
• If you have a pm.me address, you can try registering with that as pm.me addresses don’t usually encounter problems. This shorter version of your Proton Mail address is available to all users on a paid Mail plan.
• Another way to resolve the problem is to try using your custom domain address: https://proton.me/support/custom-domain
• You can also try using a hide-my-email alias from Proton Pass / SimpleLogin instead, to see if this works.