With the M4N Addon you are able to add feeds of the M4N network. So this does not work with only the regular plugin.
In M4N you have to request access to the productfeeds first. On the left site of the admin screen in M4N you will see an option called product feed. If you don’t have access yet it will ask you to use a webform to send M4N an email to request access.
If you have access you will get to a screen with all available product feeds. Behind every product feed you will see a green icon to download the feed. Click on the icon to get to a new screen for that specific feed.
This is how the screen looks like. Make sure you select XML just like the above screen shot. You will then get a Download link in the bottom. Use this link in the plugin to import the feed to your site.
When you see the message “Tailormade aanvragen” instead of the URL, which you see in above screenshot, then you need to request access for that specific feed.