Have you tried to put your username and password in the server password field in mIRC, as suggested by znc?
The server password field is the 5th editbox, after 'Group' if you're using the server list option.
@khaled this is an issue, the server list option window cannot have twice the same editbox text 'password' as that is completely misleading, one should be 'server password' while the second should be 'nickname password'
Already tried that, didnt work. I removed the ZNC account, created a new account with a new password, works now.
Something is off. Thanks anyway