Mac users with HP printers were left surprised when they recently discovered that they were no longer able to print from their devices after Apple revoked a certificate that signed HP's print drivers.
With the certificate revoked, macOS mistook HP's print drivers for malware and frustrated users began to voice their concerns over the issue online on Apple and HP's forums as well as on Twitter.
The problem itself appears to impact both macOS Catalina (10.15) and Mojave (10.14) users with HP printers. Additionally, the print queue on the affected systems now shows a mysterious “Encryption credentials have expired” message.
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According to BleepingComputer, the issue stems from the fact that Apple recently revoked the digital certificate installed on HP's printers through XProtect which allows the company to prevent Mac devices from running applications that it no longer sees as trustworthy.
Using your HP printer on a Mac
Although the issue left many Mac users with HP printers unable to print over the weekend, fortunately a fix is now available.
To get started, affected users need to remove the /Library/Printers/hp folder from their devices to delete any old drivers that have been incorrectly flagged as malware.
From here, users should open System Preferences on their Mac and head to the Printers & Scanners area. Here you'll need to double-click on your printer and select “Printer settings” and the click “Show Printer Web Page”. From the printer's web page, users will need to follow the steps from HP's knowledgebase to generate a new Self-Signed certificate for their printer. This will generate a new certificate for your printer that will be valid for 10 years.
Once this done, you'll need to return to the Printers & Scanners area, right-click on your printer and select the “Resent printing system” option. This will uninstall and remove the printer from the list and you'll need to click on the plus icon to re-add it.
Your HP printer will now be able to print normally on macOS and the “encryption credentials have expired” message should no longer appear in the print queue.
In a statement to The Register, HP provided provided further insight on the issue, saying:
"We unintentionally revoked credentials on some older versions of Mac drivers. This caused a temporary disruption for those customers and we are working with Apple to restore the drivers. In the meantime, we recommend users experiencing this problem to uninstall the HP driver and use the native AirPrint driver to print to their printer."
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