Login loop on ASP.NET application

Since October last year, our site, made in ASP.NET Framework 4.5.2, which is authenticated by Windows, has been having problems when logging in these two browsers and we fear that the error also spreads to Firefox, since sometimes it also fails there.

The specific error is that when logging in, it brings up the login screen again.

I log in with my password:

And then, the login window is shown again. .

We tried to check all of our IIS configs, to no avail.

Here are the authentication configs:

Advanced configs of the site:

Basic app pool configs:

Advanced app pool configs:

What configs are we missing?

Thank you very much!

We figured out what happened in the site.

We had to add in the registry key HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa\MSV1_0 the Multi String value BackConnectionHostNames which contained only the hosts, not with the domains, because it only read the first line of the file and the other kept on the loop.

After that, we double-checked if we had in the IIS Authentication, Windows Authentication as our only authentication active. But, in the authentication providers, we had to remove all the providers but NTLM, because Kerberos and the others weren't compatible. (It seems like there was a MS KB in October that disabled those providers)

We restarted IIS and our sites worked.