Does the local PC or server use port 4370? What's the IP address of it? Is it a static one? Can you access it using http://LAN IP:Port locally?
Read this article to troubleshoot.
http://www.tp-link.com/en/article/?faqid=785

There is currently no server or local PC that uses the port 4370. The IP address has been set to a static IP address of 192.168.1.150. Please see attached screenshot.

There is currently no server or local PC that uses the port 4370.

I'm confused. What kinds of device are you trying to open port for ?:confused:
192.168.1.150 is not IP address of any local device or server?:confused:
Why did you configure port forwarding?

I'm trying to connect a time attendance device that has a network connection which I had set a static IP address of 192.168.1.150. I have a management application that can connect the device via IP address and port 4370. I have also configured on the router a DDNS. When trying to connect the device remotely, I can't seemed to be able to get a connection. I can get a reply to the DDNS but the port is always blocked.

Sorry for the earlier confusion.

What kinds of management application?
Can you use web browser to access it?
How did you test it remotely?
Can your connect the device via WAN IP address and port 4370 instead of DDNS remotely?
Are you sure WAN IP is a public one?
( private IP range:10.0.0.0—10.255.255.255； 172.16.0.0—172.31.255.255； 192.168.0.0—192.168.255.255)