You load a fresh HP 936 or 936e cartridge into your OfficeJet Pro 9120e, and the touchscreen immediately flashes Cartridge Problem or Ink Cartridge Missing. The printer sits there, refusing to print, and that new cartridge you just snapped in doesn't exist as far as the machine is concerned.
Most of the time, this is a simple communication breakdown between the cartridge chip and the printer's reader. A few things specific to the 9120e tend to cause it. Here's the fastest way to narrow it down.
Start With the Orange Tape
HP ships 936-series cartridges with a bright orange protective tape covering the nozzles and the chip contacts. If you missed pulling it off, the printer can't read the chip at all. Pull the cartridge back out and check the bottom and the side for any leftover plastic or tape. This is the single most common cause of the not-detected error on this model, and it takes two seconds to fix.
If the tape is completely off and the error sticks, move on to the next step.
Reseat the Cartridge Firmly
The OfficeJet Pro 9120e uses four ink cartridges. Open the front door and cartridge access door, wait for the carriage to stop moving, then press the front of the problem cartridge to release it. Reinsert the cartridge securely into the matching color-coded slot, making sure the color-coded letter on the cartridge matches the letter on the slot.
If you are checking more than one cartridge, repeat the same remove-and-reinsert step for the other cartridges, then close the cartridge access door and front door.
Clean the Gold Contacts on Both Sides
If the cartridge is seated and the error continues, clean only the electrical contacts. Open the front door and cartridge access door, wait until the carriage stops moving, and remove the affected cartridge. Lightly dampen a lint-free cloth or swab with distilled water, squeeze out excess water, and wipe the copper-colored contacts on the cartridge.
Use a clean, lightly dampened lint-free cloth or swab to clean the matching electrical contacts in the carriage, then let the contacts dry before reinstalling the cartridge. Avoid touching the contacts with your fingers, and do not leave the cartridge out of the printer longer than necessary.
Unplug the Printer for 3 to 5 Minutes
Restart the printer using HP's documented power sequence. With the printer turned on, disconnect the power cord from the back of the printer, unplug the cord from the wall outlet, wait at least 15 seconds, plug the cord back into the wall outlet, and reconnect the cord to the back of the printer. If the printer does not turn on by itself, press the Power button.
Check for Instant Ink or HP+ Restrictions
Instant Ink and HP+ are separate. HP says Instant Ink subscription cartridges work only in the enrolled printer and are disabled after the service is canceled; after cancellation, you must remove Instant Ink cartridges and install regular cartridges. An active Instant Ink subscription alone does not prove that every third-party cartridge is the cause of a detection error, but any Instant Ink cartridge error should be handled through the Instant Ink account or HP Instant Ink support.
If HP+ was activated during setup, HP says HP+ requires Original HP Ink for the lifetime of the printer. Separately, the OfficeJet Pro 9120e uses dynamic security: it is intended to work only with cartridges that have a new or reused HP chip, and firmware updates can block cartridges using a non-HP chip, including cartridges that previously worked. A reused HP chip can allow reused, remanufactured, and refilled cartridges.
Update Firmware Through HP Smart
HP says firmware updates can enhance printer functionality and fix issues, and the 9120e checks for updates automatically by default when it is connected to the internet. To check manually on the printer, use Menu > Utilities > Settings > Firmware Update, then choose Auto Update, Notify, or Do Not Check. You can also open the Embedded Web Server, go to General > Firmware Update, and click Check for Update.
Swap Cartridges to Narrow It Down
If you have another compatible cartridge handy, install it in the matching color-coded slot. If another cartridge works in the same slot, treat the first cartridge as the likely problem and contact the retailer or HP for replacement options. If every compatible cartridge fails in that slot after reseating, cleaning, restarting, and updating, use the control panel path Menu > Utilities > Tools > Maintenance > Restore Settings and choose the appropriate reset option, or contact HP support.
For a genuine HP cartridge, HP's cartridge warranty applies when the cartridge is used in its designated HP printing device, the HP ink is not depleted, and the end-of-warranty date has not been reached. HP says the cartridge warranty does not cover cartridges that have been refilled, remanufactured, refurbished, misused, or tampered with.