The website uses https and uses https certificates issued by non-authoritative organizations such as self-signature. For security reasons, the use of https certificates issued by non-authoritative organizations is prohibited in iphone, so the connection is blocked. There is no solution to this, except changing the mobile phone.

The website verifies the user agent and prohibits mobile devices from accessing it. You can try to change the useragent (browser ID) of the iphone browser.

I hope this helps.