[10060] Connection timed out error More here
Scenario: Joe dialed Mary's number, but it never rang, or, it rang but she never picked it up.

Things can get slow on the Internet. Either when you try to reach a far away server or when connections somewhere in between your Internet provider and the IRC server are broken. Very often you didnt have a (proper) connection to the Internet even before you started mIRC. Patience is usually the best option here. Try it again in a few minutes or try another IRC server. This has nothing todo with mIRC. There is not something you can magically fix.

A connect or send request failed because the connected party did not properly respond after a period of time. (The timeout period is dependent on the communication protocol.)

Check the obvious first: check that the destination address is a valid IP address. If you used a hostname, did it resolve to the correct address? If the hostname resolution uses a local host table, it's possible you resolved to an obsolete address. Can you ping that hostname?

Do you have a router configured? Is the router up and running (check by pinging it, and then ping an address on the other side of it)? Try a traceroute to the destination address to check that all the routers are functioning.

Check your subnet mask. If you don't have the proper subnet mask, your network system may treat a local address as a remote address (so it forwards addresses on the local subnet to the router, rather than broadcasting an ARP request locally), or visa versa.