You would need to either set the captive portal to normal http or use a secure server for your page.
It could also be the web page your phone is initially pinging is secure and that's where the redirect is happening - can you set the ESP to log all requests? Then you'd be able to see what's going on
AFTER that happens, if connection occurs, the web page can be accessed by typing the IP address into the web browser being used wether it's on a PC or mobile phone. Almost always the pc will fail to connect giving a notification that the device is using and "old security standard" and should not be connected to. If for some rare chance the pc does connect (it then usually drops) or via mobile phone, when the web page is accessed the browser then shows the web page as insecure via icon on the address bar; however it does function as it should. I've read several blogs on the subject but haven't seen a reasolution.
In this particular project it is not my desire to use station mode through a router, as the device may not have access to a router most of the time.