Is that because you don’t see the Move in the System/Rooms tab in the Sonos App, or is it there and the volume control doesn’t appear when you select it to bring it into focus?

I see it.  I can move the volume control but there's no change in the volume on the speaker. 

That sometimes can mean the controller (or the Move) has temporarily lost connection. Do you have more than one ‘wireless’ access point that your devices may have access to, or any guest WiFi networks enabled, that the controller device might be auto-switching to/between?