imap not recognising aol account

Has you email provider (AOL) switched to using App Specific Passwords? If so, you will need to generate a unique password for your iPad email account - that will differ from your AOL Account Password.

If you need to generate an App Specific Password, you’ll need to log-in to your AOL account using a web browser - and generate the Password from the appropriate account security page.

Go to your AOL Mail account in a web browser (mail.aol.com), go to the security settings and generate a ONE TIME PASSWORD for the device you're trying to use. See here (which is not well explained by AOL at all!!): https://help.aol.co.uk/articles/Create-and-manage-app-password