O365 Portal login still redirecting to Organization sign in after changing domain from Federated to Managed

I'm trying to get our O365 login working by authenticating a pilot group that's been sync'd to O365 via the Azure Sync Tool I downloaded from the portal when I logged in as Admin and setup on a 2012 R2 server.

The pilot group, which is just one user, sync'd fine.

However, when I go to sign in at portal.office.com with my username@domain.com, it still gives the message "We're taking you to your organization's sign-in page".

It then redirects to an https://ADFS.domain.com (where domain is our actual company's domain name that's online).

So I connected via Powershell per online instructions, and ran the following command to convert the domain in question from "Federated" to "Managed":

Set-MsolDomainAuthentication -DomainName domain.com –Authentication Managed

And now it shows as Managed instead of Federated.

However every time I try to sign in in the browser, I still continue to get the "We're taking you to your organization's sign-in page" message, which lands on the dead/unavailable adfs.domain.com site.

The ADFS server it's trying to direct to is not even around anymore. It was deleted my a terminated team member from before my time.

I can't run Set-MsolADFSContext because the ADFS server doesn't exist.

Are we stuck with this forever? Do I need to contact a Microsoft tech support and is there a free line of support to fix stuff like this?