Greetings, the following two methods should solve your current issue.
try all of these realmlists.
set realmlist west.kronos-wow.com
set realmlist north.kronos-wow.com
set realmlist east.kronos-wow.com
If the change of realmlist didn't help at all then you'll have to restart your router. Should I be of further assistance, please feel free to contact me on Kronos Discord.
Regards,
Flash