Added note:
Make sure your email hasn't got junk mail filters that may have blocked the email from being received. This is often a problem. Also, make sure you typed the email correctly.
I haven't heard of any networks that allow you to resend your registration info, so as YODA suggested, ask in #Help or the equivalent channel, you may need an IRC Operator to resend the mail. Perhaps there's an #OperHelp channel or equivalent. Check out the network's website too, they often contain very good information - if you don't know the website address, search on
Google.
It's also possible that it's not your end that's the issue but rather the network...could be Services went offline after you registered, their mail servers are/were being attacked so the email just "got lost" in space as it was coming to you. Sometimes this stuff does happen!
Worth noting for future reference that mIRC nor these message boards have any affiliation with any channel, server or network. Services such as NickServ/ChanServ/etc. are completely owned by the network that they exist on, and all help regarding them really should be found on the network's help channels and through their administration. There are different Services packages out there, some networks even code their own Services, so we can't possibly know all the different commands that the NickServ you're talking about may have. Some networks don't even have Services

Hope this helps!
Regards,