Follow the instructions below in order to reconnect your Outlook (the actual program installed on your computer) to your web-based email inbox.
Potential reasons you may need to recreate your Outlook Profile:
After you have clicked "OK," you should be able to open the Outlook program and it will connect to your Office365 mailbox.
Use Office.com now instead of Webmail
Make sure that if you are trying to access your email from a web browser, you now go to www.office.com in order to login, and then click on the email link from that site.