Replacing Print Cartridge

Turns out there was an easy solution. I filed a support case and had an answer in half a day:

"Often this issue is caused by a sensor. â Therefore the first thing we should do is try to trigger the sensor.
1 Turn off the HP LaserJet 3050
2 Remove the toner cartridge from the HP LaserJet 3050
3 Remove all of the paper in the paper tray
4 Check the entire paper path for any obstructions
5 Reseat the toner cartridge and paper
6 Power on the HP LaserJet 3050

If the issue is still not resolved we will need to try some resets on the HP LaserJet 3050.
1. The first reset we can try is a soft reset, it is done by pressing the MENU key then holding *# together. â This will bring you into a Developers Menu. â Scroll through the options until you find reinit FFS and then press the ENTER key.
2. If this reset doesn't clear the issue we can try a harder reset. â We can do this by pressing MENU, scrolling over to SERVICE, pressing ENTER, scrolling over to RESTORE DEFAULTS and pressing ENTER to restore the defaults and ENTER to confirm.

WARNING: Restoring the defaults will clear your fax settings, phonebook numbers and headers so you may want to print a phonebook report and Config Report first. â We can do this by accessing the Reports menu.

3. If these two resets do not help there is a third reset we can try.This reset will completely put the HP LaserJet 3050 back to factory defaults.WARNING: Before doing this reset we will need to disconnect the power cord, the phone cable, and the USB cable from the back of the HP LaserJet 3050.We can do this reset by unplugging the power cord from the back of the HP LaserJet 3050 then holding down the MENU/ENTER key and * symbol at the same time,then powering the HP LaserJet 3050 back on with the keys compressed.We will release the keys as soon as PERMANENT STORAGE INIT appears on the display screen."

I tried all the steps in sequence; it took #3 to fix it. Fortunately I didn't have a big fax address book or custom settings, so a factory defaults reset didn't cause any extra problems. It retained the time and date, and now it works fine.

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