Are you using an older version of mIRC?

This was discussed in depth in this topic: https://forums.mirc.com/ubbthreads.php/topics/244052/Connect_to_networks

Khaled mentioned using the 'password' field for lookups in the future, I don't know if it was ever added.

I do believe there's a solution to your problem in this topic though, so please take a look and I'll try to reproduce your problems later if necessary.