Do you know what 802.11 protocol the router is? More recent protocols like 802.11ac typically won't show separate SSIDs, since they rely on 5 GHz primarily, and use 2.4 GHz as a fallback.
Is the phone not able to connect at all? Is the phone able to see the SSID? If this isn't your router, could the owner have made the SSID hidden so that other people don't try to piggyback on their wi-fi signal?