Nighthawk R7000P Connecting to only some devices

I've had issues the past month with dropping internet on devices in our home network. This has normally been remedied by rebooting the Nighthawk R7000P router. The past couple days some devices such as iPhones, iPads, and a PC based laptop will connect, but not other desktop computers, fire stick, and other misc devices. The routerlogin shows internet connectivity. The failing devices see the router for no internet connection. The ISP is Comcast and the router is Netgear CM1000. I've adjusted channels and restarted both modem and router several times. Could use a lifeline!