I guess their geo-blocking isn't up to date. If you check what IP address you're using and it's different one to last week, it could be that your ISP started using a new set of IP addresses. While waiting for e-rewards to fix it, if your ISP has multiple IP ranges that it allocates from and you just happen to have an address in one of them that e-rewards doesn't know about, you might be able to make the site happy by dropping your connection in the hope of getting an address from another range.

(Or you can use a proxy or VPN to get around it.)