It seems, many people try their luck in Freebitco.in and make someone cannot play free roll

I've got that too, and I see the same message as him, I think many people who use the same ISP wants to get the prizes hahaha
But will see it later after 1 hour, if I still get the same message then maybe I need to activate my VPN

There can be many reasons for it depending on what type of internet connection you are using. Mobile networks particularly often change your IP and the last person to use it may also be a customer. There is also a lot of malware that turns your device into a proxy server which access to is then sold.