The more devices you add to a network, the more robust that network needs to be. All routers have limits to the number of devices they can control. Combined modem/routers are often not robust enough to handle the demands of a Smart Home, as well as all of the PCs, phones, and tablets fighting for bandwidth. This is especially true if you are still using the equipment your ISP provided you with five years ago. Your router may randomly begin to drop devices when too many things try to connect at once. And it will generally drop the one it senses is not actively using the connection . It may not pick those devices back up when other, more demanding devices cease their bandwidth hogging. When you reboot the router, it now has bits and bytes for your smart Device again, and connectivity is restored. (This is way over-simplified, for purposes of this discussion. Sometimes, upgrading your equipment can put an end to random device dropping. If you ha...