Mail not updating my gmail inbox

Hello, I am having a strange behavior with the mail app. I have two gmail accounts set. The first one is updated every time I open mail and from time to time. The second one, however, is not being updated don't mather what I do. It updated when the account was setup and, cinse then, it didn't update again. I check the appropriate inbox in the mail box list and try to activate the get mail button but nothing seens to work. What should I do to have both accounts updated when I open the mail app, similar to the way it works in IOS application? Marlon