"the mail server imap.gmail.com" is not responding.... on my iPad again

..... this pops up when I try to retrieve my gmail from my iPad, and it also says in the pop up box, "verify that you have entered the correct acct. info in Mail settings...."so I click on settings and it takes me into the settings and I scrolled down to 'mail' icon (it is not a gmail icon though, just the blue envelope)... and have no clue what to do now.... when I tap on my gmail icon, it comes up but at the botrtom of the emails along the left side, it says "last updated 1/27, Account Error. Gmail [Details (in blue)] and when I click on "details" a pop up appears stating what I mentioned above.