Long running website no longer loading correctly

I have a website which has ran properly without any changes for a few years. When users type in the URL, they are to be taken to the main page if logged in via session, or taken to the login page if not logged in. As of Monday, logged-off users who type in the URL are taken into the main page instead of the login, and only taken to the login page when they click on something. My web.config file has the login form specified under authentication mode, and the main page has: If Session("Logged In") = False Then Response.Redirect("Account/login.aspx") End If

Yet none of them are catching the issue when users first type in the URL. I'm not sure what could have changed in the processing of these commands since the weekend as it has always worked before hand.

If anyone has ever experienced this before or has a good idea what the issue is I am all ears. Troubleshooting on my end has not been able to fix it.