HP Scan cannot find device, yet printing works fine to same MFP

[steverob]

Got a remote office with just a few staff all working off the same Wi-Fi network. They've got a ColorLaserJet MFP M278-M281 and can print to it fine via the IP address (same subnet), but they cannot scan - they say they used to be able to, but it stopped working a few weeks ago.

I've remoted into their laptops and taken a look, but have reached a dead-end. I uninstalled and re-installed the printer software, downloading the fully featured version from the HP website and set the printer up in Windows fine. But when I try to run the HP Scan program, it just says "The HP LJ M278M281 was not found" and an OK button, which just quits the program.

I've downloaded Print and Scan Doctor and went through the Scanning Problems wizard - it checked everything and came back with a whole list of green ticks, but then when I asked it to do a Test Scan, the same error message appeared. I can provide screenshots if needed.

Can anyone suggest what steps to try next?

[Apone]

its possible there could be a hardware issue going on with the scanner.  hit its embedded web page using its assigned IP and check the event log option for any scanner related errors.  

[steverob]

I went on to the webpage and checked the logs but couldn't find anything obvious - most of the error entries were things like paper jams.

However we have managed to now fix the problem by other means - stumbled across it by sheer fluke!  One of the users mentioned that when the scanner was working, the printer was always problematic and as now it seems to be vice-versa, so I thought we could try to treat them separately.

So I connected the user to the printer using the IP address in Windows - e.g. manually adding a new printer in Control Panel rather than doing it via the downloaded software (and using HP Universal drivers), but then used the proper HP software to connect the scanner via the Wi-Fi Direct option and magically this seems to work. Hopefully it'll stay that way!