If you have setup port forwarding on the router.
Check the hardware firewall status of the router, and at what level the security is set to.
If set to high, lower it to medium.
The test again with the port scanner software you are using.
If you still get no response or feedback from the port scanning software running on your system.
The likely cause is because you are also running a software firewall within the windows OS you are using.
Remember that for any program, game, or server you may of setup that you also need to enter or open up, or set the required ports to be opened in the windows software firewall also.
Or simply temporally disable windows firewall or windows security centre, then test to see if it is the software firewall of windows blocking the open ports from your machine to the router, and back again for incoming data or packets.
It is more likely to do with the fact windows software firewall is no causing you the problem if it still enabled and running at the same time as the HW firewall of the N600 router Darkseiders.
Have a check.
Disable windows Firewall and port scan again.