I recently upgraded to iPhone 6s, and have been unable to connect to Wi-Fi. When I try to join my network, it keeps telling me I have the incorrect password. I am looking right at the password, on the back my wireless router, yet my phone still tells me I have the incorrect password and am unable to join the network. As a result, I am down to only 10% data storage with still 15 days left in the cycle. This never happened with the prior phone.
First forget you wifk on phone if you can. The. Reboot phone and reset network setting. If that doesn't work then:
Was the password changed on the router at anytime? You may need to reset the router to factory settings, usually a small press switch in back. Everything will be wiped and reset to new Out of the box.
What was your prior phone? I would second the router reset and re-configuration, if you're positive the password is correct. Keep in mind, if your router uses WPA or WPA2 Encryption, all passwords are Case Sensitive and must include all numbers and special symbols in the password. Apple devices work best with WPA2 Encryption. Do not use WEP or WPA encryption with them.