Wifi disconnects from my home network.

My Blu has recently disconnected from my home network. This was a random occurrence as nothing in my household has changed. No new hard/software, etc. When I try to connect, it signs in, connects for a moment and then gives me a "WiFi Connection Failure" message. No other device is having a problem. I have reset the router; unplugged and plugged back in...all the 'standard' fixes. Nothing has corrected the issue. I can, however, connect to my 'Guest WiFi' in my home, same modem/router. Why can I not connect to the secured WiFi in my house? It has been the same connection for over a year, and the phone had been connected the whole time as well.