This error is due to a communication error in the printer. Since there can be several causes for this, we recommend to first reboot the Ultimaker S5 / Ultimaker S3 by using the on/off button.
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 the problem persists, it may be that there is a faulty component preventing communication. Please contact support by raising a support request above.