I'm running into a weird situation. I have two web applications, both using Windows Authentication. They are both using the default login page, both disallow anonymous access, no other special configuration.
Both site collections are publishing sites.
When I navigate to Web Application 1 (port 80), after logging in, I see the landing page for the site collection, and everything works as expected.
When I navigate to Web Application 2 (port 81), after logging in, SharePoint tries to redirect me to [MySiteUrl]/Account/Login. There is no such page, or configuration that I am aware where this is specified. Because the page cannot be found, it directs me to the PageNotFoundError screen. Oddly enough, I am authenticated, so clicking "go to the site home" link does take me back to the home page.
The situation happens when accessing it internally on the server, or externally, so I don't think it's related to Access Mappings.
This is a fresh install of SharePoint, so I'm not really sure what could be the problem.