Re: HP4780 printers:

Thank you for posting on HP Forums,

Flower_Bud is at your service.

As I understand, your old printer is giving an error message,

No worries, as I'll be glad to help you, that said, I'll need a few more details to dissect your concern & provide an accurate solution:

After replacing ink cartridges, are you still getting "Out of Paper" error message?

Are you able to make a photocopy?

Let's try these steps to resolve the issue: 

Solution one: Use genuine HP cartridges

Visit HP SureSupply to check ink or toner cartridge compatibility or purchase replacement cartridges and other supplies.

1. Go to HP SureSupply.

2. If necessary, select your country/region.

   Figure : Country/region selector

3. Follow the on-screen instructions to order new supplies or check cartridge compatibility with your printer.

You can also purchase genuine HP cartridges and supplies from other retailers.

Solution two: Remove, inspect, and then reinstall the cartridges

A cartridge error message might display if a cartridge does not have full electrical contact with the printer. Follow these steps to remove and then reinstall the cartridge.

1. Make sure that the printer is on. If necessary, press the Power button to turn on the printer.

2. Open the cartridge access door. The carriage moves to the center of the printer.

   Figure: Open the cartridge access door

3. Wait until the carriage is idle and silent, and then lightly press down on a cartridge to release it.

   Figure: Remove the cartridge

   1. The tri-color cartridge is on the left side of the carriage

   2. The black cartridge is on the right side of the carriage

4. Slide the cartridge out.

      CAUTION: Do not touch the copper-colored electrical contacts or the ink nozzles.

   Figure: Copper-colored electrical contacts and nozzles

   1. Copper-colored electrical contacts

   2. Nozzles

5. Remove any clear protective tape that still might be on the nozzles.

   Figure: Remove the protective tape

      CAUTION: Do not attempt to remove the copper electrical strip.

6. Reinstall the cartridge in the printer.

   Hold the cartridge with the HP logo on top, and then insert the cartridge back into the carriage slot. Push the cartridge firmly into the slot until it snaps into place.

   Figure: Insert the cartridge into the carriage

   • The tricolor cartridge goes into the left carriage slot.

   • The black cartridge goes into the right carriage slot.

7. Close the cartridge access door.

   Figure: Close the cartridge access door

8. Try to print again.

Solution three: Clean the cartridge and carriage electrical contacts

1. Gather the following materials:

   • Distilled water (tap water might contain contaminants that can damage the cartridge)

   • Cotton swabs, coffee filters, or other soft, lint-free material that will not stick to the electrical contacts

   • A clean sheet of paper

2. Open the cartridge access door. The carriage moves to the center of the printer.

   Figure: Open the cartridge access door

3. Wait until the carriage is idle and silent, and then disconnect the power cord from the back of the printer.

4. Press down on the cartridge to release it, and then pull it toward you out of the slot.

   CAUTION: Do not leave the cartridges outside of the printer for more than 30 minutes. If the cartridge is outside of the printer for too long, the ink can dry and clog the nozzles.

   Figure: Remove the cartridge

   1. The tri-color cartridge is on the left side of the carriage

   2. The black cartridge is on the right side of the carriage

5. Inspect the cartridge contacts for ink and debris buildup.

6. Dip a clean swab or lint-free material into distilled water, and then squeeze any excess water from it.

7. Hold the cartridge by its sides, and then clean only the copper-colored contacts.

   CAUTION: Do not touch or clean the ink nozzles. Doing so can result in clogs, ink failure, and bad electrical connections.

   Figure: Clean the cartridge contacts

   1. Copper-colored contacts

   2. Ink nozzles (do not touch or clean)

8. Repeat these steps for the other cartridge.

9. Clean the contacts in the print carriage, located inside the printer.

   Figure: Print carriage contacts

10. Wait 10 minutes to allow the cartridge and carriage electrical contacts to dry.

11. Hold the cartridge with the HP logo on top, and then insert the cartridge back into the carriage slot. Push the cartridge firmly into the slot until it snaps into place.

    Figure: Insert the cartridge into the carriage

    • The tricolor cartridge goes into the left carriage slot.

    • The black cartridge goes into the right carriage slot.

12. Close the cartridge access door.

    Figure: Close the cartridge access door

13. Reconnect the power cord to the back of the printer.

14. Press the Power button to turn on the printer.

15. Try to print a page.

16. If you are still unable to print, repeat these steps to clean and reseat the cartridges. Multiple cleanings might be necessary to restore printing.

Solution four: Reset the printer

Follow these steps to reset the printer.

1. Press the Power button () to turn on the product.

2. With the product turned on, disconnect the power cord from the rear of the product.

3. Unplug the power cord from the wall outlet.

4. Wait at least 15 seconds.

5. Plug the power cord back into the wall outlet.

6. Reconnect the power cord to the rear of the product.

7. If the product does not turn on by itself, press the Power button () to turn it on.

If the issue persists, please try these steps from the link https://hp.care/2DrVvI2

Solution five: Replace the problem cartridge (You could contact our phone support for replacement ink cartridge).

Workaround: Print in backup mode

For out of paper error, refer to this article: https://hp.care/2GvurLT.

Solution one: Perform a reset
Solution two: Check the condition of the paper, and then reload it
Solution three: Clean the rollers
Solution four: Adjust the paper settings in the print driver​​​​​​​

Keep me posted,

Have a great day

Cheers!