Plex Media Player not responding to Playback requests

I am working on adapting / extending a Plex remote control for SmartThings [ https://github.com/ph4r/SmartThings/tree/master/PlexManager ] that was started by someone else. I have the playback commands working on my Apple TV, but the Navigation Commands do not work there. My bigger issue right now is that no matter what I am trying I can not get Plex Media Player [PMP] to accept either set of commands either bouncing the command through the PMS with a X-Plex-Target-Client-Identifier (as works on the AppleTV4 App) or with direct communication to the PMP IP And Port as listed in the devices.xml response. I can see from the log file that the client is recieving my command (either method); however, it always reports an error of “2017-01-08 09:17:50 [ DEBUG ] HTTPServer.cpp @ 165 - Incoming request to: “/player/playback/pause” from “10.10.10.23”
2017-01-08 09:17:50 [ WARN ] RemoteComponent.cpp @ 268 - Can’t find a X-Plex-Client-Identifier header” despite me verifying that I am also sending this header (tried with appending the header the same smartthings method as other keys, and also with “?&” or just “?” appending on the path request).

Please identify if this is an invalid log message, or if there is something I am missing?

I have PMP and PHT working now for sending commands and getting back timeline status information. However, the same approach that I see from the official API documents are not working for the TVOS App or Roku. I can see from my app that the Apple TV returns from my timeline request that it is unable to connect to my host, but nothing further. Since other hosts are able to connect, I’m a little confused.