Minimum temp error is hot bed.
Firstly, pls check whether the thermostor of hot bed is ok or not?
Second, pls check the wiring connection of hot bed, as the following image:
If one of the metal port is out, the cable could not work.
Third, pls check the hot bed wiring connection of mainboard, right wiring?
as the following image:
If the above two tips are good connection, the reason is A14 port of mainboard is broken.
Cause the thermistor of hot bed connect A14 port.
There is a spare port, A15, in the mainboard, you need reflash the firmware to change A14 port to A15 port.
Pls send us your 3d printer model no. or the order link, 3DP-08,11,12,17,18?
And then, the correct firmware would be sent to you soon.
It would be fixed.