Ok... did have a closer look.
From your log...
PlayVideo requests this...
as port 32400 was found during PlexGDM.
However your server - according to MyPlex - uses a different port (discover):
... port="23963"
Which one is correct? To me, it looks like PlexGDM is faulty.
Also, your two servers have completelly different global IPs... are the both connected to the internet? Do they share the same home-net? This kind of confuses me...
Short term solutions...
option 1) disable PlexGDM and specify your local server manually.
option 2) disable PlexGDM and manually select a non-existing server, thus only relying on MyPlex.
option 3) fix your Waterfront PMS to show the correct port...
option 4) log out of MyPlex... though, I guess, your server's port would still show up wrong.