The venue's network admin said they weren't filtering anything outbound to the Internet. We could access websites from the iPad just fine. Same w/ Facebook, Youtube, etc.
I put up Mitmproxy, an adhoc Wi-Fi network on a second Wi-Fi NIC, a DHCP server, and iptables NAT on my laptop. I set the iPad to use my adhoc SSID and my machine as an explicit HTTP proxy. My intention was to snoop on the traffic to determine what Mevo was using for criteria to consider being "connected".
For whatever reason the Mevo app just started working in this configuration. I ended up sticking a spare Wi-Fi router and a PC w/ Mitmproxy installed in the venue for the duration of the event. I never did figure out what the Mevo app didn't like about the venue's network.