UpdraftPlus cannot currently be used with a Google account with enhanced security protection.
Could UpdraftPlus submit for approval if eligible?
URL: https://support.google.com/accounts/answer/7539956#zippy=%2Ccan-i-still-use-sign-in-with-google%2Ccan-i-use-non-google-apps-services-or-apps-script-with-advanced-protection
The Advanced Protection Program performs additional security checks to safeguard your account data, and it hasn’t approved this app.
If you want to allow UpdraftPlus access to your data, you can reach out to the app developer and encourage them to submit the app for verification. Learn more about this error
If you are a developer of UpdraftPlus, see error details.
Error 400: policy_enforced
This idea was posted in UpdraftPlus - backup/restore plugin on September 30, 2022 by 
racetrade2017.
Hi,
Thanks for this idea. I have added it to our internal task tracker to get someone to look into what’s involved.
It’d be helpful if you could give some more information on your side. Why do you use this program – what are its benefits? It’s helpful for us to understand customer use cases and motivations.
Thank you,
David