Hi,
if the password has changed for a WIFI profile and you change the password in the WIFI config of your mobile
it's not possible to connect to the WIFI network again.
You can only connect to the WIFI network again if you drop the WIFI config on your mobile and reconfigure it with your new password.
We've experienced that issue in our company on about 32 mobiles (Z3+Z3C on 5.1.1.) .
Looks like the old password is still stored.
Cheers,
Michael