If your email account is IMAP or Exchange, then the easiest thing to do is to delete the account and re-add it. Since everything is stored on the email server, it will sync back to the iPad.
However, if you are using a POP account, more precautions are required. Deleting the account on the iPad will do one of two things. The emails and folders for that account will be deleted forever, or you’ll end up downloading every email from way-back-when as if they were all new. Depends on how you’ve configured your POP account clients.
Hotmail, Office 365, Outlook, and other Microsoft email flavors use Exchange servers.
Gmail, Yahoo, and most other third party email services are IMAP.
Many email accounts included with ISPs (Internet Service Providers) like Verizon, local cable companies, etc. default to POP accounts. Some offer IMAP, but you need to manually choose the IMAP server. Best to check with the providers support site to be sure.
Note: Yahoo is IMAP when configured on an iOS device. Yahoo on a computer client is POP if you do not have a paid account. At least they did last time I checked. It’s usually easier to use the web client on a computer.
That said, the Mail client is supposed to prompt you for the password when it can’t make a connection. I’ve also heard that the Accounts & Password settings will give you a password field under the account if the password hasn’t been working. It does not normally show up.
You can try restarting the iPad and see if either of the above starts working.
