Hotend not heating on new vcore 400 Build

Hi all,
Hope you're all doing well and thank you in advanced

I have just finished up building my vcore 4 500 full kit supplied by RR
Everything but the hotend is working, I'm getting a temp reading from the thermistor which is working correctly (tested this manually warming it up with a hair dryer) but when I try to heat the hotend it just doesn't heat (throws a klipper error stating it's not heating)

I've triple checked wiring and all is good - is there any tests I can do to make sure it's not a dud hotend?

Thanks
Mike