Welcome to the HP Forums, this is a great location to get assistance! I read your post and see that you are getting "Door Open" error message on your HP HP Officejet 4500 Printer. I would like to help you resolve this issue.
Close the cartridge door completely.
Check the cartridge door for obstructions.
Reset the product.
Press the Power button (
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) to turn on the product.Disconnect the USB cable from the back of the product.
Disconnect the power cord from the electrical outlet.
Disconnect the power cord from the product.
Wait 30 seconds.
Reconnect the power cord to the electrical outlet.
Reconnect the power cord to the product.
Press the Power button (
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) to turn on the product.
) to turn on the product.
) to turn on the product.Click here and refer the document to perform the above steps.
Let me know if that works.
Cheers.