If you have been 'blocked' or 'barred' then that is nothing to do with mIRC. You will have to contact the network administration to have the block lifted. Sometimes, entire ISPs are banned due to the abuse from one person (constant ban evasion for example) or a small group of people. Therefore, you may not have much luck getting the ban removed.
You'll need to go to the network's website. If you don't know the website, search Google
For some more information on this issue, look in this thread
Best of luck getting back online.