I believe this could be either DNS or Proxy. They may be using different DNS (manual or automatic) but to confirm this is the case they need to be having problems with other sites as well.
Regarding the proxy, which is my situation, it needs to be configured. So, if they have configured it, they need to take a look at it. In any case, to access and continue betting, just access this link that I mentioned earlier and see if they can access any of them. If you have any questions, just let me know!
I believe the default DNS that is needed to get access to all websites is 8.8.8.8
I don't think it will work but I have some chrome extension which I found are good with preventive measures as after downloading them I have never face any issues in accessing those platforms.
I will share those extension if someone is facing issues as to how getting access to a banned site without any issues. I might be wrong about it but, after I had installed those extensions, I am able to view those websites that are banned in my country.