Having the same issue for day. Hotspot is in AP mode, connected to the hot spots wifi, Safari just sits there loading. I've been on this for a few days and same results. I do not do this at home because I do not want the home network to interfere.
Do you mean that the openSPOT3 is in AP mode, and the web interface won't open automatically? If yes, enter http://192.168.99.1/ into Safari. Note that this address is only active while the openSPOT3 is in AP mode, indicated by white status LED.