If a device is filling out forms but you are not seeing the data back in CometEZ, there are two things you want to check for.
Make sure the device is in coverage and/or connected to a data network. Because the forms transmit over the devices internet, if the device is out of coverage or not connected to a Wi-Fi, it will not be able to submit the form data. If you feel the issue is with the device, please contact your wireless carrier or device supplier. Remember all form data is stored in non-volatile memory. This means that all previous form data cannot be erased unless the app in uninstalled, so as soon as it connects properly, all the previous forms will be sent without any data loss.
Also, make sure the device can get a gps position. Because the device tries to associate a gps location with a form, some reports will not show data that has not been associated to a location because the form has not been fully processed.