Hello, I am Scottish and have an account with the British National Lottery. For years, I paid and played this game through my National Lottery account without any trouble using my PC, but recently, when I try to log in to my account with them, they no longer recognise me and tell me that I live outside the United Kingdom. How can that be? I don’t think my IP Address has changed. Strangely, when I use my laptop, I am able to log into the site without any problems. Can anyone out there shed any light on what has happened, or have they encountered this problem before? Any help would be appreciated. Thank you.
It sounds like an IP/location detection issue rather than a problem with your account. 
Your ISP may have changed your IP or its geolocation data may be incorrect.
Since the laptop works, check that both devices are on the same network and try disabling any VPN/proxy, clearing your browser cookies/cache, or using another browser. 
If it still happens, I’d contact National Lottery support so they can check the location flag on your account. 