When a max temp error on the build plate occurs, it means that the build plate sensor reads a temperature that is higher than the maximum value set in the firmware of the printer. This can either be caused by a bad connection to the heated build plate or main board, or by a damage in the heated build plate cable.
To resolve this issue, the following check is recommended:
Check if the heated build plate cable is properly connected to the heated build plate. The cable is connected at the back side of the build plate, with four thinner (white) cables at the end. Gently pull them to see if none of the wires if loose. If one of them is loose, the heated bed has to be removed in order to re-connect the cables.
If the error still appears while the cables are connected properly and after rebooting the printer, there might be a damage in the electronics. In this case we recommend to get in touch with one of our local service providers for assistance.