Some possibilities: - if using a VPN, turn it off - check that cookies are acceptable at settings>privacy&security

Thank you David but neither of these options worked for me.

Ok, I am not the Gmail guru, and I regularly see posts of problems in setting up Gmail accounts. My suggestion is to remove the account completely and start over. And this time, do not enter password during the setup process, but wait until the Google screen pops up and asks for it. No guarantee, but it usually works for me.