I now solved one problem
Since I am running MB in Swedish, I needed to change "Everyone" to "Alla" (Swedish for Everyone). Then cmd accepted the phrase.
Everything went fine. I connect to the Chromecast and it shows a little blue chromcast icon on my tv. But when playing music there is no sound on my tv speakers (or connected hifi system). When starting the music on MB, the chromecast icon on the TV change to a moving circle, like it's waiting for something. I can see that MB is playing the file and the soundwave is changing. So it's probably trying to send sound through through the network to the chromecast. And the sound doesn't get through. After one minute the circle icon change to the blue Chromecast icon again. Sort of connected and ready. The MB is still playing, but no sound on my laptop neither. When I choose Disconnct from Chromecast, MB stops playing the song.
EDIT: When pressing the Chromecast button, the volume of MB goes down to zero. That's why I didn't hear it on my laptop. So even though the icon change on the TV to moving circle when I start the music, like MB is trying to send soemthing, it's play the sound on my laptop. Since I got the Chromecast blue icon when connecting, I suppose the MB connected, which also the Status shows. Just that it doesn't get the sound through when starting a song.
So MB sends the music to Chromecast, but the sound doesn't get through
Checking the chromecast status in MB everything is OK.
Chromecast Connection: OK
Library Set: OK
Server Running: OK
I tried the troubleshooting nr. 2 check, but I don't find the files on my browser.
"If you hear the connection sound, but no music is playing, you most likely have an issue with your port forwarding on the webserver. A good tip to try is after connecting to a chromecast, go on your phone and enter in a browser the <machines IP>:<Port#> e.g 192.168.1.27:8080. If you're able to see the files, then the chromecast will be able to as well."
So, please, anyone knows what's wrong? Everything is fine, but no sound...