Due to the problem of spamming on anonymous IRC servers, all users by default have server side ignore set.
This means that only people on your accept list are able to private message you. You can remove this setting from
your session by removing mode g.
Alternatively you can remove mode g and set mode G to automatically accept messages from users you share a channel with.
You can edit your accept list by issueing these commands:
When somebody who is not on your accept list tries to message you, you will receive a notification.