Signature verification failed #26606 (MK4S) #13606 (MK4) #27606 (MK3.9S) #21606 (MK3.9) #28606 (MK3.5S) #23606 (MK3.5)

Relevant for:

MK4 MK3.9 MK3.5 MK4S MK3.9S MK3.5S

Last updated 3 hours ago

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What happened?

When trying to install non-official firmware on your Original Prusa MK4/S, MK3.9/S, or MK3.5/S, the screen shows "Firmware signature verification failed! Only official signed firmware can be flashed".

Error name: Signature verification failed

Error code: #26606 (MK4S) #13606 (MK4) #27606 (MK3.9S) #21606 (MK3.9) #28606 (MK3.5S) #23606 (MK3.5)

The error is issued when your printer has detected an attempt to flash firmware that does not have the private key signature that verifies the firmware as being official.

How to fix it?

The Original Prusa MK4/S, MK3.9/S, and MK3.5/S in their factory state only accept official firmware. In order to flash a custom firmware, you need to break the appendix seal on the xBuddy board.

Breaking the appendix seal won’t void your warranty, so you are free to flash custom firmware.
However, since there is no way for us to verify or test every single custom firmware on the internet, we disclaim liability for any kind of damage or harm a printer with a broken seal may cause (e.g. in case of a fire).
So, please, don’t mindlessly flash suspicious files!

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