What router are you now using? Does it have any parental control software enabled (to block gaming) or do you use Plusnet Safeguard for parental controls at all?
You say you cant get to the website or speedtest.net either? Can you get to any other websites?
Can you try running a traceroute to their site? tracert www.blackdesertonline.com (on windows) and we can see where it stops compared to others. I can get to the website fine at the moment.