Gmail login, mail download and upload works fine on my laptop at home, on my home network, but away from home - no chance....
Away I use another laptop, usually via a mobile network, with my phone acting as an hotspot. Google sometimes, only sometimes emails me to my ISP email address, to which access is OK - and warns me it might be an hacking attempt, with a link to their website. I click OK to say it is me trying to login, but each login attempt still gets rejected.
Not sure if it is complaining about me using a different laptop, or a different network to login to grab mail.