Browser displaying cached files instead of redirecting

I have a problem with AppCache.

The problem is this. I have a site that is cached, which requires a VPN connection or a 3rd party login to access. If you enter the site while on VPN everything works fine.

However, if you access the site without being on VPN you are supposed to be redirected to the 3rd party login page, but instead the browser shows a half broken page of cached files.

If I load the page without VPN in Incognito mode then the 3rd party login page is shows just fine.

Has anyone solved this before? Any idea how to redirect to the login page instead of showing what is cached?