@Lisa_Loo, Welcome to HP Support Community!
Ensure that the printer is up to date with its firmware and Mac is up to date with its software. If you are unsure you may use the links below to update the printer firmware and Mac software:
Update printer firmware
Update software on Mac
Try scanning.
If the issue persists, we can try updating the HP Easy Scan App. Here us how you do it-
Uninstall the printer software and reinstall it. Refer to the document HP Printers - Uninstalling HP Printer Software (Mac) for help. Once you have the latest software, try scanning.
Hope this helps! Keep me posted.
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TEJ1602
I am an HP Employee