RTP/WebRTC: Video streaming from FFmpeg.exe, NO video with C++ FFmpeg Library

[Robot FFmpeg]

Hello,

I have set up a Janus server.

I CAN view WebRTC video, when I stream RTP using FFmpeg.exe, from my local computer. I can see the resulting WebRTC video at [MY-SERVER-IP]/streamingtest.html

I CAN NOT view WebRTC video, when I stream RTP using the C++ FFmpeg library, from the same local computer. I can NOT see the resulting WebRTC video at [MY-SERVER-IP]/streamingtest.htm. Instead, The webpage states "Plugin Demo: Streaming", "Started - 276 kbs,  No remote video available".

I do not think this is a STUN/ICE/TURN issue, as I am able to stream RTP to Janus from the same computer using FFmpeg.exe. I also do not think the issue is AWS/EC2, as I have followed the instructions to avoid such problems, and I can successfully stream RTP to the server from the same computer.

The successful RTP FFmpeg.exe command is:

 ffmpeg `
  -v info `
  -fflags +genpts `
  -protocol_whitelist pipe,tls,file,http,https,tcp,rtp `
  -stream_loop -1 `
  -re `
  -i C:/Users/tomsh/Downloads/x264_720p_baseline.mp4 `
  -map 0:v:0 `
  -c:v libx264 `
  -x264-params intra-refresh=1,fast-pskip=0 `
  -threads 3 `
  -profile:v baseline `
  -level:v 3.1 `
  -pix_fmt yuv420p `
  -tune zerolatency `
  -minrate 500K `
  -maxrate 1.3M `
  -bufsize 500K `
    -f rtp `
rtp://[MY-SERVER-IP]:6004?pkt_size=1316

I *think* I have set the same above parameters in my program that uses the C++ FFmpeg library.

Question:
Is there a way to debug Janus, or "debug" the rtp stream, to help me figure out what h264/RTP setting(s) I have misconfigured?

Server: CentOS 7 AWS EC2

Janus: Latest from SNAP