HP Smart Tank Plus 555 with 00 error code

[ClaireDk]

My HP Smart Tank Plus 555 was initially coming up with 00 error code and now can't find the printer. I've tried turning off and on with 3 second hold, restarting printer and Mac

[Hawks_Eye]

Hi @ClaireDk 

Welcome to the HP Support Community! We're here to help you get back up and running.

The “00” error code on your HP Smart Tank Plus 555 typically indicates a firmware initialization failure or a stalled startup sequence. Since the printer is now undetectable, it’s likely stuck in a non-responsive state. 

Let’s walk through how to recover it and restore connectivity.

Step-by-step actions to resolve “00” error and reconnect your printer

Perform a full power reset

• Turn off the printer and unplug it from the wall
• Disconnect all cables (USB, Ethernet, etc.)
• Wait at least 60 seconds
• Plug it back in and power on with no cables attached
• If the display still shows “00,” proceed to step 2

Try a forced firmware recovery

• On a Windows PC (if available), download the latest firmware from HP:
  HP Smart Tank Plus 555 – Firmware Update
• Use the HP Printer Update Utility to create a recovery USB
• Insert the USB into the printer while powered off
• Power on and wait—if the printer accepts the update, it may reboot automatically

Check for hardware lock

• If the printer remains stuck at “00” and doesn’t respond to power cycles or firmware attempts, the internal controller may be locked
• This typically requires a service-level reflash or hardware inspection

Try reconnecting via HP App

• On your Mac, open the HP App (replacing HP Smart)
• Remove the printer from the app if listed
• Tap Add Printer and wait for it to appear
• If it doesn’t show, confirm your Mac and printer are on the same Wi-Fi network

This guide include illustrations and model-specific recovery options.

• HP Smart Tank Printers – Blinking Lights and Error Codes

Let me know if the printer shows any signs of life after the USB attempt or if the display changes—I’ll guide you through next steps. 

You’ve done everything right by restarting and checking connectivity, and we’ll make sure your printer gets back to full function.

If my response helped, please mark it as an Accepted Solution! ✅ It helps others and spreads support. 💙 Also, tapping "Yes" on "Was this reply helpful?" makes a big difference! Thanks! 😊

Take care, and have an amazing day!

Regards, 

Hawks_Eye

[ClaireDk]

Thanks for your help. Tried a few of your suggestions and in the end I checked paper size of the document, which was American letter. It did start printing once I changed the doc to A4. It totally confused the printer! I'll remember that one...

[Hawks_Eye]

That’s a brilliant catch, @ClaireDk—and I’m genuinely impressed you traced the issue back to the paper size mismatch. 

The “00” error is usually firmware-related, so discovering that the printer was reacting to an incompatible document format is a rare but insightful find. Switching from U.S. Letter to A4 likely resolved a silent conflict in the print job queue that was stalling the startup sequence.

You’ve not only revived your printer—you’ve added a valuable tip to the troubleshooting playbook. If it ever acts up again, feel free to reach out. You clearly know how to dig deep and solve smart.

Take care, and have an incredible day ahead! 

Regards, 

Hawks_Eye