With MTH remotes no longer available this will be a real issue in the future if the MTH DCS Wi Fi system does not work reliably. When I do not find engines on the electronic phone or devices I check the Wi Fi connection status and it says connected only to the MTH Wi Fi network not the home network. You do have to make sure that the device does not have another app open looking for a Wi Fi signal.
Sounds like a device problem. My DCS works reliably with the app. I've read of problems with certain releases of device software conflicting with this. The device must stay on the MTH WIFI and not revert to the house's router. It even matters how you shut down the system. Mine will revert to the house router if the DCS system is shutdown before the device is. So I always turn the device off first at the end of the session.
When the grandkids brought over their Apple devices, it threw me a loop at first. I run all android. One of the devices is older and it even drops the house router's pass word every time he comes over? I've had to learn a little about IOS to keep them running.