Thanks for taking an interest in the HP Support Forums! After reading your post I see that you are unable to scan to your computer from HP Photosmart 6520 printer. I would like to help you out with this issue today.
Restart devices and check driver scan settings.
Run the Print and Scan Doctor.
Uninstall and reinstall the printer software.
Check Windows Image Acquisition settings.
Temporarily disable firewall software on the computer.
Click here and follow the document to perform the above mentioned steps.