That's an app glitch when it says "Mobile Order is not available at this time." That happened to me several times and I finally asked a CM at Cosmic Ray's what was going on, because I was getting that message and people were walking up and picking up orders just fine, and he said "I don't know why you are getting that message, because mobile order is working fine." Same thing happened to me at Woody's Lunchbox. I was so annoyed seeing people placing and then picking up orders while my app said it was unavailable. And for people wondering, I asked a few people "when did you place your mobile order?" Everyone I asked said "just now." So, these people hadn't preordered the stuff awhile ago. It's an app glitch. For what it's worth, all the people picking up mobile orders at Woody's had iPhones. I have an android.
Last week at
Disneyland, when the site was having issues for a couple hours (this was a known disneyland.com site problem), I had issues placing a mobile order at just ONE restaurant. The menu wouldn't come up. All other places worked fine. I had a conversation with the guy in front of me in line because he asked me if mobile order was working on my phone. We were comparing notes and found we had the same issue just at that location, so whenever things like that happen, it's a glitch.
The restaurants don't have the ability to "turn off" mobile ordering.