When this error appears it means that the print head and electronics cannot communicate properly with each other. This is most likely due to a faulty connection between the print head and electronics.
Often, a cause for this error a poorly connected print head cable. This may have occurred during transport of the printer. Fortunately, this can easily be checked by reseating the printhead cable:
Note: The above video uses the printhead of an Ultimaker 3. However, the procedure is the same for the Ultimaker S3 and the Ultimaker S5.
If reseating the cable does not solve the issue, continue troubleshooting by swapping out the printcores. It may be that there is a bad connection between the printcores and the printhead PCB. We recommend wiping the back of the printhead PCB with an alcohol cotton swab.
If the problem persists, it may be that there is a faulty component, such as the printhead cable. Please contact support by raising a support request above.