In common with many other Mail providers, AOL now use App Specific Passwords to access IMAP or POP3 mailboxes. Your update triggered the need to update your Mail settings.
The Mail App on each of your devices, such as your iPad, requires a unique password to be generated from within the AOL account. This App Specific password intentionally differs from your AOL account password - and can only be used to access your AOL mail.
More information about AOL’s App Specific Passwords can be found here:
https://help.aol.com/articles/allow-apps-that-use-less-secure-sign-in?guccounter=1