This means your access is being denied as your location is being determined as outside of the UK. We are a UK-only site, so you will be locked out of your account if your Internet location suggests you are abroad, as per our regulations.
If you are abroad, you will not be able to play until you are back in the UK. If you have problems playing once home, please contact our Customer Support Team.
If you are in the UK, but are getting this error message, you may need to reset your Internet router. If you turn this off for 5-10 minutes, this should refresh your connection and place you back in the UK.
Also, having a VPN enabled can also hide your location. Disabling the VPN should allow you to access your account again.