Changed yesterday from U-Verse back to Cox. Using a brand new Air Port Time Capsule. No iOS device will connect to home wifi. All upgraded to IOS 9 except one and none will connect. Interesting, work phone (also upgraded) has no problem (5S), but iPad 2's and brand new 6S's will not connect. My son's 6 will not connect either. No problem with my MBP or MBA.
Attempted resolutions:
Re-booted router
Re-booted modem
Refreshed network settings on the problematic iOS devices.
Searched internet for solutions.
MacBook
Pro, OS X Yosemite (10.10.5)