iMessage does not send over Wifi

Hi all ... for some reason, I'm not able to send any messahes using iMessage on my iPhone 6 Plus (iOS 9.2) at my home's Wifi network.

When I send using 3G mobile network, the message is sent without problems, but over home Wifi the message freezes on "Sending..." and nothing happens.

Here's some info that may help:

Device: iPhone 6 Plus - iOS 9.2

Router: TP-Link N600 TL-WDR3600

Followed this tutorial to forward ports -> Using FaceTime and iMessage behind a firewall - Apple Support
Screenshoot of my ports forwarded -> http://s4.postimg.org/i7rnc0sa5/image.jpg (used my router's IP 192.168.0.1)

I did not try using other Wifi network yet, I'll try as soon as I have an opportunity to do so.

THanks in advance!