this error returns when trying to oauth.

Hi madan,

Thanks for reply. I have read about that process, but little bit confused about register localhost. 

You need to go through verification process before you launch your app, this new process came recently to protect user's data. you can start verification by submiting this form but before it is recommanded to follow steps here

 

please go through the bellow link.

https://support.google.com/cloud/answer/7454865