Rostock Max V2 with new e3d hot end installed no longer reaching temperature

[Detailedhotgluegun]

Hello,
I currently have a Rostock Max with a e3d v6 hot end installed. I was having an issue during a long print (37 hours) after installing the hot end where it would stop feeding the PLA and the temp for the nozzle read as "def" this happened a few times and I attempted to adjust some things and try the print again ... Same issue. Yesterday when I was attempting to begin the print hot end wouldn't heat up at all , it climbs very slowly in temperature never reaching more than 10-20 degrees above room temp. I re did all the wiring and replaced the thermistor and the element, still not working. I have a hunch it may be the power supply, but do not know exactly how to check / what steps to take to troubleshoot it. Any help appreciated.