So guest CAN vote as you stated above. Sounds like the issue you are having is why can't you vote as a guest on your phone AND laptop. 

It could be that the vote is logging the IP Address too. So if you are at home and have internet access via router/modem, and both your laptop and mobile device is using the same "internet connection" (your home internet), then you are only broadcasting 1 public IP Address to the web. Although every device has it's own INTERNAL IP Address, once they leave the router/modem, only 1 IP address is used.