Ok Got it working @cyn If you are using max2play update the squeezelites to the newest under the Audioplayer Tab // Edit Advanced Options // Tick Update SqueezeLite (no option to update the multi squeeze though 
) I also run a squeezelite on a couple of Macs so same thing update those as well.
You need to change your base URL to a HTTP not a HTTPS with the SSL it will not work! I have no idea why not but I ran round and round with this and now I have them working!! You will need an External address as your base URL for sure though, To test you could just set up a Port forward rule to your HA and plug in your external IP as your Base URL and test.
I saw that you posted the other day so I decided to give this a try and figure it out and Viola! I got it working.
If you plan on using for announcements look at this thread The Script will stop the play back and restart it, except on Pandora it might just restart the station. But still awesome If you have a station but not playing it will play the Audio then put the station back for the next time AWESOME! Thanks @smazman