After spinning up the site from a back up I came across the issue with the login page not displaying correctly.
In fact it looks like the login page it trying to load the same resources but from two different URLs (example below).
GET /Portals/_default/default.css?cdv=270 HTTP/1.1
GET /DesktopModules/Admin/Authentication/module.css?cdv=270 HTTP/1.1
GET /Account/Login?ReturnUrl=%2fPortals%2f_default%2fdefault.css%3fcdv%3d270&cdv=270 HTTP/1.1
GET /Account/Login?ReturnUrl=%2fDesktopModules%2fAdmin%2fAuthentication%2fmodule.css%3fcdv%3d270&cdv=270 HTTP/1.1
What has me puzzled is the /Account/Login URL that I have never seen before.
Every request from /Account/Login URL results in 404 which is to be expected.
What is interesting is if I go to the /Login page when I am signed in the page appears fine and I have no /Account/Login requests.
This is not the first install that has been restored from a back up but this is the first one that came up with this strange issue.
If anyone has come across the issue before please let me know if you ever found a solution.