The print dialog in the screenshot below will show the error "Encryption credentials have expired." If you find a similar issue, the solution can be found below.
On Mac OS devices you will be unable to print or scan. The above dialog will appear every time you try either action.
To resolve this issue please follow the directions outlined in the document "'Encryption Credentials Expired' Error Displays". The directions will talk you through creating a new self-signed server certificate with a valid expiration date.
Resetting the certificate is the preferred method of resolving this issue. If resetting the certificate does not work, please try adding the "AirPrint" driver following the directions from the below post. Note do not select the "Secure AirPrint" option as this will cause the expired credentials error to appear.
You will be selecting the "AirPrint" option sending your print data unencrypted. This has to be done on all affected Mac devices to enable print or scan to work.