Note: If this happens only with Genie CLIENTS, the problem may be related to this FAQ instead.
First, be sure that your mobile device is connected to your home WiFi network and confirm your Whole Home settings if someone else may have changed them. An even more likely cause however is that the receiver is setup to use what is called DHCP. What this means is that your home network's router assigns it an arbitrary IP address whenever it needs to be renewed. Sometimes it happens to assign the same address, but often times it does not.
To correct the problem, you can usually just re-scan for receivers in the app. Note though that if your receivers are in fact using DHCP, then you may want to consider configuring your receiver for a static IP address or DHCP Reservation. Static or DHCP reservation applies not only to DirecTV receivers but also is recommended for any network device you'd like to control, including TVs or AVR.
It's also worth mentioning here that I have had some reports of DirecTV receivers and even AVRs (A/V Receivers controlled by the Volume Plugin) suddenly not being detected or controllable with the app. While at first glance it appeared to be a problem with my app, the problem actually resolved itself after rebooting the DirecTV receiver or AVR itself. So if things seem like they should "just work" but they are not, consider rebooting your DirecTV receiver or TV/AVR!Tags: Scanning, Setup