Hi, welcome to iPF!
Go to Settings - Mails, Contacts, Calendars and tap the account there. If there's a limit set up (like: Mail Days to Sync), then change it to "No Limit", if possible.
Sometimes the Mail app needs some time to receive all emails, when an new account is set up. What you could try is to scroll down as far as possible. Either you'll find something like "Download Mails from Server", or you'll notice that your account is trying to upload emails (top left, the rotating little circle on the screen). If this happens, give it a little time.
You could also try the usual fixes when something isn't working as it should:
Restart your iPad: turn it off, wait for a few minutes, turn it on again.
Reset it: press and hold Home and Power button until the Apple logo appears.
Force close apps:
iOS 6: double tap Home button to reveal multitask bar, then tap and hold one of the app icons until they start to wiggle, delete the apps.
iOS 7: same procedure to reveal multitask bar, then slide thumbnails above app icons towards the top of the screen.