Problem: After installing an HP LaserJet Pro MFP over the network on Windows 10, the Scan to Computer option on the printer won't find the computer.
Cause: The Windows Firewall is blocking the connection and/or the HP installer is installing the printer in a way that Windows 10 doesn't recognize it as a scanner.
1. Disable the Windows Firewall, then test. Continue if the problem persists.
-> Instructions: https://support.microsoft.com/en-us/help/4028544/windows-10-turn-windows-defender-firewall-on-or-off
-> I do not suggest doing this unless you have a firewall protecting your entire network on your router or other firewall device.
2. Go to Control Panel\Hardware and Sound\Devices and Printers
3. Rename your Printer to something else (right-click->Printer Properties)
4. Choose Add Printer near the top of the Devices and Printers screen.
5. Let it detect your device, select it from the box, and click Next to install it.
6. You will now have an additional device, when you right-click it you will have some scan options which you may not have had with the printer installed by the HP installer.
7. Your computer should now show when you use the Scan to Computer option on the printer.
The HP Scan application was not designed to work with Windows scan functionality. Therefore it cannot be selected as a default scan action. You will need to use the built-in Windows Fax and Scan, or install another app that integrates with Windows in this way.
Because of these limitations the "Scan to Computer" option from the printer Control Panel in a networked setting is rather unsatisfactory. It makes more sense to load your material and launch HP Scan, or if you need quick scan and save/send functionality, use Scan to Email or Scan to Network Folder instead.