How you send the message? Where is your game objects where you want to send your message to?
It might be just wrong addressing.
For easiest addressing:
print("My url: ", msg.url())
in init() in the script, to which you want to send your message.
This is the easiest way to get to know the correct absolute address of this script (so recipient’s addrress) 
That way, you can use it to write correct address in msg.post(), but please, read more about addressing:
Or if you prefer videos, I have another one for you! 
I also have a library called Pigeon, that simplifies sending messages - in each recipient you must though subscribe to given message, but instead you don’t care about addressing - Pigeon just sends the message to subscribers (yep, there’s also a video about Pigeon on my channel, but enough of shameless plugs I think, google it ;D )