Elegoo Neptune 3 Plus - Temp too Low -14

Hello,Any ideas or advice much appreciated.Had problems with this printer. Started getting thermal runaway error for which Elegoo recommended PID tune. Did this and it seemed to fix the issue. However, then had major blockage which melted PLA all over the hot end. Was such a mess that I decided to replace the hot end. Bought genuine Elegoo replacement hotend. Attached it, now error is Temp Too Low check for short circuit. Nozzle temp reads -14. Replaced thermistor on new hot end but same error. Pretty much ready to junk the whole thing.Thanks