HP6978 connected by cable only does not find computer after clearing paper jam. (Worked before.)

[JM1209]

HP 6978 has always been connected directly to computer by cable, with wireless disabled.  Not on internet.  It has always worked fine this way until after clearing a paper jam.  While clearing jam person disconnected printer-side USB and network cable without first turning off  printer.  After restarting printer it gave warning message that printer had not been turned off properly.  Now with all cables reconnected it says "Not connected to any device".  Disconnected and reconnected USB and Network cables, and tried restarting printer while connected, while disconnected etc., as well as restarting the computer.  (Have checked connections to both printer and computer before retrying each time.)  None of that fixes. We do not intend to connect wirelessly. 

[Max3Aj]

@JM1209, Welcome to HP Support Community. 

Thank you for posting your query, I will be glad to help you. 
I understand your HP OfficeJet Pro 6978, which is connected via USB and not using wireless, stopped recognizing your computer after a paper jam was cleared and cables were unplugged while the printer was still on. Let's work through this together.

Power Cycle the Printer and Computer

• Turn off the printer and unplug the power cord from the wall.
• Shut down your computer completely.
• Wait for 60 seconds.
• Plug the printer back in and turn it on.
• Once the printer is fully powered up, turn on your computer.

Check USB Cable and Port

• Ensure the USB cable is securely connected to both the printer and a working USB port on your computer (preferably a USB 2.0 port if available).
• Try a different USB port on your computer.
• If possible, try a different USB cable to rule out cable damage.

Verify Printer is Detected by Windows

• On your computer, press Windows + R, type devmgmt.msc, and press Enter.
• In Device Manager, expand Universal Serial Bus controllers and Printers.
• Look for any entries related to the HP 6978 or any Unknown Device (which might indicate a driver issue).
• If found, right-click and uninstall the device, then unplug and replug the USB cable to reinstall.

Reinstall HP Printer Software

Sometimes the driver may become corrupted after an improper shutdown. Reinstalling can help:

• Go to the official HP Software and Driver Downloads page:
  Official HP® Support
• Download and install the Full Feature Software and Drivers for your operating system.
• Follow the on-screen instructions and choose USB connection when prompted.

Disable Wireless (Optional)

Since you’re using USB only:

• On the printer control panel, go to Settings > Network Setup > Wireless Settings.
• Make sure Wireless is turned Off.

Additional Tips

• Avoid unplugging cables while the printer is powered on to prevent firmware or connection issues.
• If the printer still shows “Not connected to any device,” try connecting it to a different computer to isolate whether the issue is with the printer or the PC.

I hope this helps. 

Take care and have a good day. 

Please click “Accepted Solution” if you feel my post solved your issue, it will help others find the solution. Select "Yes" on the bottom left to say “Thanks” for helping! 

Max3Aj

HP Support