Tried for months to get my Amcrest Camera to work with IP Cam Viewer with no luck. Found the answer.
1. Amcrest Cameras come with default port of 37777. If you want to use more than one with IP Cam Viewer, you must make them different
2. When you write your Port rule for the router, you must put in 80 for Local Port. External port or port range will be the port you assigned above. Rob briefly mentions this in his camera setup post, but it isn't very clear.
After I did that, my Amcrest cameras started working with IP Cam Viewer.
Regards,
John