I'm trying to add a new gmail account to mail on my mac but a 400 error comes up

Appsy1 wrote:

Authorisation Error

Error 400: invalid_request

You can't sign in to this app because it doesn't comply with Google's OAuth 2.0 policy for keeping apps secure.

You can let the app developer know that this app doesn't comply with one or more Google validation rules.Sign in with Google

Authorisation Error

Error 400: invalid_request

You can't sign in to this app because it doesn't comply with Google's OAuth 2.0 policy for keeping apps secure.

You can let the app developer know that this app doesn't comply with one or more Google validation rules.

Learn more•

Request Details

The content in this section has been provided by the app developer. This content has not been reviewed or verified by Google.

If you’re the app developer, make sure that these request details comply with Google policies.

redirect_uri: urn:ietf:wg:oauth:2.0:oob

The very first sentence tells you what the issue is.

2nd sentence tells you what you need to do.

this isn't an Apple or imac issue.

Appsy1 wrote:

Hi I'm not real good a this stuff How do I fix the problem please

As stated in the 2nd sentence in your post, contact Google and let them know.