Hello, and thank you for choosing JA for your support needs. I am happy to assist you with this issue.
What is the make and model of the HP Printer in question, Sir or Madam?
Invisible Paper JamWhen you have a paper jam in the front of these machines the printer doesn’t always report a paper jam message on start up. The sensor only covers a small area so, often times, the paper debris doesn’t block the sensor flag. I’ve seen it happen both ways.
In situations where the paper is not blocking the sensor flag the machine will boot up to a ready state then, when it goes to print, the paper will feed up several inches and give a paper jam message. In most cases, when the cassette tray is pulled out, half the paper is in the machine. In cases like this you will still need to follow the instructions in the link below instead of just running it through the middle of the paper path you need to run it on the sides also.
This also works with the 500 Series: