Not the phones fault ..Reset and then Log in to Router via your PC Review WI fi settings and resew/a new pw.
I do this all the time..w/o the histrionics.
BobD -- there is truth to what Mattb67 said.
I recently bought the HTC One and my wife the Iphone 5. Neither would connect to my Actiontec GT724WGR modem/router, which is less than 4 years old. All other peripherals in my house connect just fine to that modem/router.
I happen to know a lot about networks, and after resetting the router, trying different modes and channels, making sure firewalls were off, and trying a complete restore, and checking that firmware was latest, neither of those two phones connect to it with WPA or WPA2 security.
Fortunately I had an old 2Wire 2700HG-D router in basement and the two phones connect just fine to that wifi. I since tried the Actiontec again, and still no-go.
Unfortunately, that Actiontec modem/router has trouble connecting to modern cell phones via security methods that have been around for 10+ years. Quite ridiculous.
What fixed my HTC One was changing the encryption method of my wireless router for WPA-PSK from AES to TPIK. I discovered this was the issue by turning off the security on my router...the HTC One connected immediately. I then turned on the WPA-PSK with AES encryption and I received the same issue...the phone kept trying to authenticate over and over again as if a wrong password was supplied. Because I knew the password was 100% correct (all other devices in my house were connected and operating correctly with the same password), I figured it was the security (in this case the encryption type) that was keeping the phone from connecting. NOTE: I have an ancient Belkin router (Model: F5D7230-4). Good Luck! I hope this helps.