Our iPhones are saying wrong wifi password

My wife and I each have an iPhone 6 and we are having the issue of "wrong wifi password". We've had this problem before, but it was a simple fix of forget network and signing back on. This time nothing is working. I've tried everything . . . Firmware updates on the router, resetting network settings, entering Mac addresses, Every tip and trick I have been able to find online. It will connect from time to time and work for a few minutes before disconnecting. All other wireless devices are working fine with no issues. The latest update which claimed to fix wifi issues did the exact opposite for me, I'm ready to throw these phones out the window.