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Hi
Don't know if you have fixed it? In Google chrome go to the three dots right corner, choose settings, notifications, turn off. Worked for me.
It's gone now. Google took the warning away after a waiting period of two weeks. But thank you for your suggestion my friend.Certainly realize that the warning just might be true - - someone is attempting to compromise your account.
Obvious actions are to change your password AND to activate two factor authentication.