How are you connecting to it? You should be able to connect using Bluetooth, but the Move may need to be turned on or woken up first.

When you first set it up it was on wifi. 
At the park you’ll need to use Bluetooth and pair it with your phone. 
https://support.sonos.com/en-us/article/pair-sonos-move-2-with-bluetooth

Yes when I first set it up it was on WiFi 

Can you Bluetooth pair but then no music plays? Or does it fail to pair? Are there any error messages?

You’re really not giving much information for us to try to help you. 

It's a deliberate feature to prevent you from inflicting your noise on others in a public space.

Is it a permanent feature, or is there a selector somewhere, to toggle it on/off?

Are you trying to use the Sonos app to play music when away from your home network?  The Sonos app has no role to play in this scenario.  You need a music playing app and you must connect to the Move over Bluetooth.  Is that what you have been trying to do?