Hi Michael,
Thanks for posting in the community.
According to your description, the built-in feature Scan to SharePoint in the HP printer didn’t work. May I know whether users are able to access and save files on the SharePoint sites?
If the issue only exists using the built-in feature Scan to SharePoint, based on my search, please try the methods in the reference to troubleshoot the issue. Check if it helps. If the issue still exists, since the issue is related to the HP printer, I would like to suggest you contact HP Support for help.
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If the issue also exists in users accessing and saving files in the SharePoint sites, please point it out and let me know.
Appreciate your understanding and patience.
Regards,
George