Can't log in via Gmail app but browser login is fine I can't log in through my android Gmail application and have to log in using the browser. I am kind of confused. The response I got from the app was "Can't establish a reliable data connection to the server".
Here are some things you can try to get things working right:

1. Try an alternate data connection. 


  Try other data connections, preferably faster WiFi, if available.


2. Check your devices Date and Time.


  Either wait for your service providers to set date and time automatically or you can manually update the time by Settings &gt; Date &amp; time


3. Reset your Google apps.


  
  Go to “Settings” > “Applications” > “Manage applications” > “Google Apps“, then tap the “Clear data” button.
  Go to the Home screen.
  Select “Settings” > “Data synchronization” > “Google“.
  Enter your Google credentials.