SUMMARY
When trying to add a new Gmail account, google accounts denies the "Akonadi Resources for Google Services", because it is not verified as a compatible app for working with "Access with Google"

STEPS TO REPRODUCE
1. Download KMail
2. Select "add account", fill in with the email and password and click next.
3. The account wizard will find the config online, and it will select the gmail config
4. Press add account, and a pop up will appear, in which you may log in to your google account in order to connect Akonadi Services For Google Services with your google account.
5. After the log in, there is the error, saying that the app is not compatible yet with google accounts.

OBSERVED RESULT
When syncing gmail and "Akonadi Resources for Google Services" (when the "add account" button is pressed), an error pop ups saying "Akonadi Resources for Google Services" is not verified yet to work with "Access with Google"

EXPECTED RESULT
Log in and sync emails without problems. 

SOFTWARE/OS VERSIONS

Linux/KDE Plasma: KDE Neon 5.17.1
(available in About System)
KDE Plasma Version: 5.17.1
KDE Frameworks Version: 5.63.0
Qt Version: 5.13.1
KMail version: 19.08.2