Are you perhaps attempting to use the Method Classic desktop site from your iPhone? If so, this is certainly the cause of your issue. Please make sure that you are using the mobile site on any mobile devices, as the Method Classic desktop site is not compatible with mobile browsers.
If you are already doing this, you could try clearing your browsing data from safari:
Clear information from your device
To clear your history and cookies from Safari in iOS 8, tap Settings > Safari > Clear History and Website Data. In iOS 7 or earlier, tap Clear History and tap Clear Cookies and Data.
To clear other stored information from Safari, tap Settings > Safari > Advanced > Website Data > Remove All Website Data.
Please let me know if the above helps you to resolve the issue. Otherwise, I recommend you give support a call at 1.888.925.6238 x2 and we can take a closer look at this.