Just a few tips from me that have helped me with various online games.
Disable IPv6
You can test if you are able to establish a connection to our service when IPv6 is disabled:
Go to the Control Panel.
Click Network and Internet > Network and Sharing Center > Change adapter settings.
Select the connection for which you need to disable IPv6. For example:
To change the settings for an Ethernet connection, right-click the Ethernet interface and select Properties.
To change the settings for a wireless connection, right-click the Wi-Fi interface and select Properties.
In the window that appears, select the Networking tab.
Under This connection uses the following items,
remove the checkmark next to Internet Protocol Version 6 (TCP/IPv6) and then click OK.
In many cases, this fixes the connection issue. Should you find yourself still being unable to connect,
please move on to the next step.
Google DNS
It can happen that an Internet Service Provider’s (ISP) Domain Name Service (DNS)
is temporarily unable to resolve our URL into an IP.
To verify that this might be the case, we recommend switching to Google’s DNS.
To do so, simply go again to the Networking tab in the window from earlier.
This time, select Internet Protocol Version 4 (TCP/IPv4) and click Properties.
In the new window that appears, select Use the following DNS server addresses:
8.8.8.8
8.8.4.4
The other problem that might be relevant is that they have a killer network card,
that needs to be configured in the Killer Control Centre according to application priorities.