The out-of-band (OOB) flow has been blocked in order to keep users secure.

[johnnyjosefsson]

Seems the app requires to be updated in regards of the auth process due to new minimum security aspects from Google

Access blocked: PROJECTS’s request is invalid
users
You can’t sign in because PROJECT sent an invalid request. You can try again later, or contact the developer about this issue. Learn more about this error
If you are a developer of PROJECT, see error details.
Error 400: invalid_request

Error 400: invalid_request
The out-of-band (OOB) flow has been blocked in order to keep users secure. Follow the Out-of-Band (OOB) flow migration guide linked in the developer docs below to migrate your app to an alternative method.
Request details: redirect_uri=urn:ietf:wg:oauth:2.0:oob

https://developers.google.com/identity/protocols/oauth2/resources/oob-migration

[jayhendren]

I received this error when using mbox2gg on a remote server with the --noauth_local_webserver flag. Apparently whatever feature allowed this flag to function is no longer supported by Google. I got around the issue by downloading my .mbox file to my workstation and running mbox2gg without that flag, which opened up an authorization page in my web browser.

[KrzysztofHajdamowicz]

Unfortunately, today it's not possible to use copy-paste, application have to listen on :8080 for auth token.