If you are using a fairly standard account like gmail, icloud, hotmail, etc, then removing and re-adding the account will almost always clear up any issues. Because these accounts store everything on their servers, nothing will be lost. Basically any account that uses IMAP or Exchange is safe to re-install. ISP specific accounts are often not, as they tend to cheap out and use the older POP3 service.
But first, if you have not done so, try powering the iPad down and on again. It is easy to forget that iPads, just like other computers, need an occasional reboot.