Have you turned off the internet connection ???
The Media Server was originally an PC / Mac app only with the internet settings pages as the player. The software we are using today (Squeezelight) was bild in to streaming receivers and therefore born with an IP address as the only option to receive music.
So if you have turned off wifi your Squeezelight is trying to connect to the last known IP adresse.
To make your Squeezelight software see your Media Server on your Pi with out an internet connection you must set up an access point.
This is quit easy with Max2play:
You can find a plug in for that
I hope this will help