With your google account, do you have two factor authentication enabled?
If so you will need to create an application specific password for use with Grafana, once done this can be entered into your config.
This link explains how to do that:
https://support.google.com/mail/answer/185833?hl=en
I have this working on my RPI 3 at home, if you need further help I can upload my config when I am at home.