how to open port 3389 on DIR-655

I try to RD my server from outside of my office by using DDNS service. The router that i use is Dlink DIR-655 model, i have already set port forwarding that is port 3389 to my IP server but when i checked the port at www.canyouseeme.org the result shown that; it could see the service on IP on port(3389). So how should i set up the router to make the web checking see the port?
                                                                              Thank you in advance for the answering