Also tried: removing WPA security, adding Mac address of bulb from the hub settings, updating bulb firmware via temporary hotspot connection.
On some forums it says to try and change the DNS to 188.8.131.52. but in order to that I'd have to put the hub in modem mode and connect another less-resistrictive router. Even this hasn't worked for everyone
Could you add some more information on the fix for this, I have the same issue and can connect to the guest network without password but the lights still wont connect to the main2.4ghz wifi. did you disable the 5.0ghz. which security settings did you use?