You can install our site as a web app on your iOS device by utilizing the Add to Home Screen feature in Safari. Please see this thread for more details on this.
Note: This feature may not be available in some browsers.
If you use VPN on your phone, try connecting with VPN disabled. Also, if no VPN used, try connecting with WiFi on and off to determine if WiFi or mobile data could allow to connect. Other than that, I dont have other suggestions