Unable to access remote DVR

Hi there,

We are facing a very strange problem when accessing a remote site CCTV DVR. When we connect that particular DVR from our office (using Comcast Business), we cannot see or load the remote DVR on to the CMS (central monitoring server), the system says "device is offline". Initially we thought it has something to do with the remote DVR setup, but upon checking, we can browse to the remote DVR web portal from cell phone apps through AT&T and T-Mobile network. We then suspect it has something to do with the CMS server itself, but when we disconnect the CMS server from our network and connect it to the Xfinity Public Hotspot (which we can connect to from our office), the CMS can load and view cameras from the remote DVR without any problem. However when we re-connect the CMS server back to our network, the problem occurs.

We bypass the firewall and connect the CMS server directly to the Comcast Business IP Gateway (SMCD3G-CCR) and give the CMS Server A fixed public IP provided by comcast, problem remained the same. 

Since we can connect to the remote DVR through the Comcast Xfinity Hotspot, there shouldn't be a routing issue between Comcast Network and the Remote site (running on Way Port broadband internet service), right? But how come we we cannot connect to th eremote site from our office's Comcast connection? 

Any help or suggestions is greatly appreciated.

Joe.