I went to a site that I had mapped on sensorly the previous night, but was not able to connect. The network screen was clearly showing LTE but my mobile network stayed disconnected. Toggle didn't work, power cycle didn't work. I also tried to disconnect the mobile network and reconnect and it would do a stutter to connecting. connecting then fall back to disconnect.
I'm pretty sure this site was not blocking connections because when I drove away and started to toggle again eventually it connected and I turned back around and mapped some more. Today I had the same thing happen at another site too.
I was under the impression that if they blocked the connection you would still have 3G (in my case I had no data at the site unless I toggled to CDMA only, at that point the mobile network connected)
I also have a EVO LTE but this sounds different from the other issues people have had. It wouldn/t default to 3G at all