You can go to the edit connections dialog to view the password in plain text and compare it to the one entered in the failed-connection dialog.
If the password stored is not the one you have entered, you have found a bug, that the entered password is not stored.
You can try to change it in the edit connections dialog, if it is wrong.
Then verify if the password has actually been changed.
I have experienced such a problem together with Bug #1542733 with a ubuntu 16.04.1 LTS live cd.
You can go to the edit connections dialog to view the password in plain text and compare it to the one entered in the failed-connection dialog.
If the password stored is not the one you have entered, you have found a bug, that the entered password is not stored.
You can try to change it in the edit connections dialog, if it is wrong.
Then verify if the password has actually been changed.
I have experienced such a problem together with Bug #1542733 with a ubuntu 16.04.1 LTS live cd.