The Mac computers store your network password information locally in the "Keychain".  When you change your Q password, it is NOT automatically updated in the keychain which will cause an authentication problem when you try to print on Uniflow/Canon Copier.  

Here is how to resolve this issue.

Keychain entry deletion

1. From the Mac desktop, select "Go" from the menu bar and then select "Utilities" from the drop down list.

2. On the Utilities screen, select "Keychain Access"

3. Please search for Uniflow. This key name will be the same as the printer name. Double click on the keychain item

4. Another window will open up

5. Click on the Show Password and you will be prompted to enter your Laptop’s password.

          Enter your password you use to unlock your laptop.

6. Your keychain password will be shown. Now you can edit and save the new password. This password is the same as the Q login password.

You should be able to print to Canon/Uniflow now.

PS: You will have to cancel any documents sent prior to the above update. You can cancel any document prints giving "Hold for authentication" and reprint

This process will need to be repeated every time you update your Q password (normally every 3 months)