Google Mail has a very strong security layer, and if you access your email in a different country, that might be flagged by Google as an attempt by a hacker to access or compromise your email. Google will then temporarily shut down your account until you prove that you're not a hacker.
So if your Gmail suddenly stops working on your phone, iPad, Tablet or laptop (for example you repeatedly get asked to enter your email and password, or some other error message appears) then you should log into your Gmail via a web browser. After you have successfully logged into your account via a web browser you should be able to use Gmail normally on your device.