Per Microsoft, this issue is now resolved.
Microsoft is continuing to work on the issue. In the meantime, here are a few workarounds:
Office 365 Email – go to outlook.office365.com/mail/. It may take one to two minutes for email to load.
Teams – use https://teams.microsoft.com
OneDrive for Business – use https://iowa-mysharepoint.com
Sharepoint – use https://iowa.sharepoint.com
Some users may be intermittently unable to view or access Microsoft 365 apps in Office 365 web app.
Users receive a message "New to Microsoft 365? This is your Microsoft 365 home page—where you can see and access all of your apps. If it's empty, it could be that your user license was very recently assigned to you. Wait 10 minutes and refresh this page. If you still don't see any apps, contact your IT department. They can help you get up and running."
ITS is looking into the issue