Scanning no longer works (just after windows update)

[Je12ryb]

Just after a scheduled windows update on 13/07 (KB5015807, and servicing stack 10.0.19041.1790), my printer disappeared, and I could no longer print or scan. It looked as though the drivers were unavailable (as reported by 'Add printers and scanners')!

Support assistant, and then Print and Scan Doctor were not able to connect to the printer, even though it was connected to the network and had an assigned IP address. 

I was able to re-add a printer using the control panel 'Devices and Printers', so now I have 2 differently named printers pointing to effectively the same place - the original one not working, and a new one, presumably using windows drivers. I can now *print* using the new printer.

However, I cannot *scan*.

Since the removal of Flash a while ago, I've been scanning perfectly well using a shortcut which invoked: 

C:\Program Files (x86)\HP\Digital Imaging\bin\hpqkygrp.exe -n"#Hewlett Packard#HP Photosmart C309a series#1605992466" -a SCAN -fSCAN_DOCUMENT, as detailed in a post in an HP forum (https://h30434.www3.hp.com/t5/Scanning-Faxing-Copying/HP-Solution-Center-does-not-work/m-p/7933933/h...)

Using this shortcut now returns the error 'The scanning software was launched with improper command line arguments' 8, [(-1,0,0)]. The registry entry defined in the referenced post no longer exists, (and the parent registry entry appears to have been updated on the same date as the windows updates...). 

I feel like I should be able to re-install the original drivers, but unfortunately have mislaid my install CD, and the HP site doesn't appear to have the s/w + drivers, presumably because its an old model. I *may* have them in a backup, but wouldn't know what they were called to install them manually.

Am I safe to try to simply re-add the missing SoftwareCUEContextID entry to the registry to see if that fixes scanning, although if the original drivers are unavailable, I'm not sure that would help.

Any advice / suggestions greatly appreciated, or if anyone can provide a link to, or ISO for the orig/HP s/w and drivers.