"Cannot get Mail" The user name or password for imap.gmail.com is incorrect iOS

For iOS if you are using Apple configurator to setup gmail make sure you follow these steps.

https://discussions.apple.com/message/26827218#26827218

If you followed the steps above and still getting the incorrect username or password error make sure you have IMAP enabled on your gmail account.

Still if the issue persists then in your google/gmail security settings make sure you have enabled the Allow less secure apps flag.