Alexa cannot stream from plex server
I'm currently running the latest PMS (188.8.131.5223) and have just bought an Echo Dot specifically to use with Plex - and I am struggling to get to get working.
PMS remote access is fully configured and I can access from anywhere on the internet either through browser (https://plex.tv/....), iOS or Amazon Fire Stick. The Lovely green padlock shows against the server in all my clients. Secure connections on PMS are set to 'Preferred'. Only port 32400 is exposed through my router. Checking on the server, plex is listening on 32400, 32401, 32600.
Alex skill is linked, and Alexa is able to browse my library, list what is On Deck etc (when "preferred" secure connections set on PMS).
When I try to play a song, Alexa says "I cannot stream music unless you have enabled secure connections on your PMS". When I change my PMS secure settings from "Preferred" to "Required", Alexa fails completely and cannot connect at all, and errors with an "Uh oh, something went wrong".
When I access my PMS over https directly on the LAN (and not via https://plex.tv) I of course, get an untrusted certificate warning.
Is this a common problem?
Do I need to open additional ports for the Alexa Skill to use?
Thanks all..... it's driving me nuts !