the touchscreen on my deskjet 4155e is totally unresponsive, i can't press any buttons.

Diagnosis

The unresponsive touchscreen on the HP DeskJet 4155e is typically caused by a "firmware hang," where the printer's internal controller board encounters a logic loop or a corrupted temporary cache. This often occurs during an interrupted HP+ cloud update or when the printer enters a deep sleep state and fails to wake the capacitive touch layer of the control panel. Because this model relies heavily on a constant connection to the HP Smart ecosystem, a handshake failure between the local hardware and the cloud service can cause the UI to freeze while the rest of the printer remains powered. You can confirm this is a software freeze rather than a hardware failure by checking the power LED. If the power light is solid or blinking but the screen does not react to any touch input—including the "Home" or "Back" icons—the issue is almost certainly a crashed control board. If the screen is completely black and does not illuminate upon startup, you may be dealing with a power supply failure or a disconnected ribbon cable, but in 90% of cases, the hardware is functional and simply needs a hard logic reset.

How to Fix It

To resolve a frozen interface, you must perform a "Hard Power Drain" to clear the volatile memory (RAM) and force the firmware to reboot from a clean state. Follow these exact steps:

1. While the printer is still powered on, press the Power button on the control panel (if it responds) or simply leave it as is.
2. Reach to the back of the printer and physically pull the power cord directly out of the printer's power inlet port. Do not just turn off a power strip; the connection must be severed at the device.
3. Unplug the other end of the power cord from the wall electrical outlet.
4. Wait for exactly 60 to 90 seconds. This is critical because the internal capacitors on the DeskJet 4155e motherboard hold a residual charge that can keep the "frozen" state active if you plug it back in too quickly.
5. While the printer is unplugged, press and hold the power button for 15 seconds to discharge any remaining electricity from the capacitors.
6. Plug the power cord back into the wall outlet first, then firmly seat the cord into the back of the printer.
7. Power the device on. Allow the printer to complete its initialization sequence (you will hear the ink carriages move) before attempting to touch the screen.

If That Didn't Work

• Perform a Factory Reset via HP Smart: If the screen is still unresponsive but the printer is connected to Wi-Fi, open the HP Smart app on your mobile device. Navigate to "Printer Settings" > "Advanced Settings." This will open the Embedded Web Server (EWS) in a browser. From here, go to the "Settings" tab and select "Restore Factory Defaults." This wipes the corrupted cache that may be causing the UI hang.
• Check for "Ink Low" Lockout: In some rare instances, a critical ink depletion error or a "Cartridge Problem" can lock the UI. Open the ink cartridge access door and remove both the black and tri-color cartridges. Wait 30 seconds and re-insert them firmly. Sometimes the physical act of triggering the cartridge sensors forces the UI to refresh and display an error message, which "unfreezes" the screen.
• Clear the Paper Path: A microscopic piece of torn paper or a jammed carriage can trigger a "Critical Error" state that freezes the UI to prevent hardware damage. Open the rear access door and use a flashlight to ensure no debris is obstructing the carriage path. Clear any fragments and restart the device.
• Update Firmware via USB: If the freeze is caused by a failed wireless update, the UI will remain dead. Connect the printer to a PC using a USB-A to USB-B cable. Use the HP Support Assistant software to check for a firmware update. Forcing an update via a wired connection often overwrites the corrupted firmware segment causing the screen freeze.

Heads Up

• Avoid Power Strips: The DeskJet 4155e is sensitive to voltage fluctuations. Plugging the printer directly into a wall outlet rather than a crowded surge protector prevents "brown-out" conditions that frequently lead to UI freezes.
• Disable Auto-Update: If you experience frequent freezes, use the EWS (Embedded Web Server) to disable automatic firmware updates. This allows you to manually trigger updates when you are present to monitor the process.
• Clean the Screen: Use a dry, lint-free microfiber cloth to clean the screen. Oil buildup or dust on the capacitive surface can create "ghost touches" that make the printer appear unresponsive when it is actually reacting to a smudge.
• Ink Compatibility: Ensure you are using genuine HP 67 or 67XL cartridges. Third-party chips can sometimes send conflicting signals to the control board, causing the software to crash during the "Ink Check" phase of booting.