Changed web adaptor name, portal cannot validate ArcGIS Server services URL

[MKF62]

I believe the URL that Portal is using to reach my rest services is incorrect due to me having to unregister and reinstall a web adaptor because Builder configured it incorrectly somehow. During reinstallation, I entered a more helpful web adaptor name so the services URL Portal is trying to validate is incorrect, therefore I reach this error:

ArcGIS Server services URL 'https://FQDN/server' cannot be validated against 'https://FQDN/server/rest/info'. If the service URL is a proxy URL verify it is accessible to clients.

It could be that this URL is actually correct and I just don't realize it because I originally had named the web adaptor "server," but when I hop on the server machine and try anything with "server" appended to the end, I can't reach my services. I can reach them with the correct web adaptor name with my FQDN or my website domain name. How do I get Portal to recognize the new web adaptor name for Server?

I tried adding a new server site with the correct web adaptor name but it said it was already registered.

I did find this workaround, but I'm hesitant to use it because I don't think that's the problem. https://support.esri.com/en/technical-article/000022369

[MichaelVolz]

As per the article is Authentication on your server web adaptor currently set at Anonymous Authentication Enabled and Windows Authentication Disabled?

Is your portal web adaptor setup in reverse to your server web adaptor in terms of Anonymous and Windows Authentication?

[MKF62]

Yes - here are the setting in IIS, both the Portal and Server web adaptor have these settings:

On Portal these are the login settings I could find. My users use ArcGIS Built-In accounts, they do not login to the Portal with Windows credentials:

[MKF62]

I never found a solution to this, my guess would be to just unintstall enterprise altogether and reinstall it would probably work. Perhaps unfederating and re-federating would be another possible solution to try as well. My "solution" ended up being unfederating my server with portal because I realized we needed it to be unfederated anyway for other reasons.