If you are having trouble connecting to a particular IRC network, the solution in almost all cases is to try a different server on that network until you find one that works for you.
If you are unable to connect to any servers on a particular IRC network, it may be that the IRC network is experiencing problems in which case you would need to contact the owners of that IRC network to ask for help. The only way to find out who the owners of a particular IRC network are is to use Google to search for their name, website, network, and so on.
If you are unable to connect to any servers on any IRC network, you may be running anti-virus or firewall software that is blocking mIRC and preventing it from connecting. You would need to add mIRC to the allowed or exceptions list of your anti-virus or firewall software to allow it to connect.
