Q: iphone 6 plus still won't connect to wifi, after troubleshooting

I just got an iphone 6 plus, and when I got it home & finished the setup, it connected to my wifi just fine.  After about an hour of not being used, I couldn't access the internet on the iphone.  I turned off wifi, and the internet worked just fine.  Then I turned wifi back on, and it wouldn't join my wifi network anymore!  My other devices (PCs & iphone 4) have no problem connecting to the same wifi network, so I know it's not my router.  I have tried the following to troubleshoot the problem:

- removed other devices from the wifi network

- restarted iphone 6

- reset network settings in iphone 6

- turned off wifi networking (under system services in location services)

- turned wifi off then on (both with wifi networking on & off)

After all of the above, the iphone 6 will still not connect to my wifi.  Anybody have any suggestions??