If you have forgotten your NCI password you can follow these instructions from the IT Help Centre.
It is usually advised to wait 5/10 minutes after changing your password before you try to login again with your new password. If your login is still not working you should try clearing your cache in your browser history.
If login issues persist after following the above instructions you should "Submit a Request" with the IT Support Hub which can be done at the top right corner of the page.