Hi Connie H, I know how frustrating it is when your email just stops working on your iPhone especially after an update when you expect things to run smoothly.
Remove the Outlook account and clear saved credentials then readd it using the official Outlook.com option with Microsoft signin. If it still fails reset network settings check MFA or device compliance and as a fallback use the Outlook app or verify mailbox health in Outlook Web.
When you readded the Outlook account on your iPhone did the Microsoft signin page appear or did it auto complete without asking for credentials?
Best regards
Lucky