Hi Nitesh,
I have just tested this issue at office. I factory reseted an IAP 305 with firmware 6.5.1.0-4.3.1.0. I have powered it up by a kit power, without connecting the Eth uplink port.
1 - The IAP boots and the power LED starts flashing, after a while the radio LED starts flashing and the instant SSID appears.
2 - Both LEDs keep flashing (no one steady), I can't connect to the instant SSID (it lasts a lot and finally is connected like "without internet"), if I try to reach the WebUI I can't.
3 - After a while, the radio LED turns off and the instant SSID dissapears.
4 - IAP starts again in step 1.
After this, I powered off the IAP and powered it up again, this time I connected the Eth uplink to a LAN with DHCP server enabled. After a while, the power LED is on (without flashing) and the radio LED flashes. I can connect to the instant SSID and I can reach the WebUI successfully.
So it seems when the IAP is not connected to a DHCP server it can't get a valid IP and then the instant SSID doesn't properly work (in fact, the IAP boots from step 1 to 4 again and again), then users can't reach the WebUI. It seems for things work properly, the IAP needs to get a valid IP address.
Regards,
Julián