Hello gelo.. You may try these steps.
-Open No-ip Program -> File -> Preferences (And there will be a window that pops out).
-Under Network Adapter -> Change "Windows Default" and Click your router's name. (Ex: D-Link etc-etc)
-Now after changing your network adapter, Click "Detect my IP using remote methods".
-Now, after that Close the window, And Click "Refresh Now" button.
Note: Your IP must be dynamic. How to verify it? Then here are the other steps.
-Login to your Router, and look at your WAN ip. Now Compare your Router's WAN IP to your NO-IP's IP client, If those IP are the same then congrats! If not then let me know, there's still another method to make your friend connect to your server
EDIT: I put some screenies on comparing IPs from the Router and NO-IP client.
(These steps are based on my experience)