I had the same problem with the "red" not connected. There were also no servers listed under the servers section. After messing around with different setting for a bit, I finally started over. This will cause you to lose any custom configuration in MyMediaForAlexa such as playlists, etc.
Delete the docker by clicking on the MyMediaForAlexa icon under DOCKER and chose remove.
Delete the MyMediaForAlexa folder by going to SHARES >> appdata select the folder and select DELETE.
Disassociate the MyMediaForAlexa skill from your Amazon account from the Alexa app on your phone
Go to APPS and reinstall MyMediaForAlexa. I accepted the defaults and added the path to my music files.
After the docker starts, go to a browser and http://IPADDRESS:52051
Log into the Amazon account you want to associate with MyMediaForAlexa using a web browser (this help the next step go smoothly)
The initial screen should prompt you to associate to your Amazon account which you just logged into previously.
This was the key step for me and then it shows a green "connected" and the servers section was populated again.
Add the MyMediaForAlexa skill back to your Amazon account from the Alexa app on your phone
A few other things I learned while testing:
Specifying Network Type Custom:br0 and giving it a different IP Address on your subnet also works.
The appdata share can be configured as Export "No" and Security "Private" and still work.