Be aware that your iPad4, although updated to the most recent supported version of iOS for this model, is obsolete - as is the 32-bit Operating System and system architecture upon which it is based. Your iPad4 and available Apps might not now support the security and network protocols that the Microsoft servers now require.
The majority (if not all) Microsoft productivity Apps now require iOS/iPadOS14 or later. Your iPad4 cannot support any more recent than iOS 10.3.3/4.
If you are instead using your iPad’s built-in Mail App, you are likely to need an App-specific password to access Microsoft Mail services. In common with most major mail providers, AOL, Yahoo, Google and Microsoft all use App Specific Passwords when using anything other than their own email client Apps. The App-specific password intentionally differs from your regular account password.
If you need to generate an App Specific Password, you’ll need to log-in to your Mail Providers account management webpage - using a web browser - and generate the Password from the appropriate account security page. Once the password has been created, you’ll need to update your mail settings with the App-specific password.
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
For Yahoo, more information can be found here:
https://help.yahoo.com/kb/SLN27791.html
For Gmail:
https://support.google.com/mail/answer/185833?hl=en-GB
Microsoft:
https://support.microsoft.com/en-us/account-billing/using-app-passwords-with-apps-that-don-t-support-two-step-verification-5896ed9b-4263-e681-128a-a6f2979a7944
