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.
If a USB stick was inserted into the Ultimaker S5 when the error appeared, the log files were automatically stored on the USB stick.
If there was no USB stick inserted when the error occurred, please insert a USB stick, and navigate to Preferences > Maintenance > Save log files to USB.
Please contact your local service provider for help and send all log files to your support contact, so they can provide further assistance.