Turn on advanced mode and you can add up to 5 different Wi-Fi networks per configuration profile. According to the user manual:
http://manuals.sharkrf.com/openspot2/en/network-page.html#wireless-settings
If Advanced mode is enabled, you can define up to 5 Wi-Fi networks (per configuration profile) to connect. If the first configured Wi-Fi network is not available, then the openSPOT2 will try connecting to the second one. If it's not available either, then it'll try the third one and so on. After trying connecting to all of the configured networks, it restarts the sequence with the first network.