I saw that you weren't asking for technical advice, but that won't stop this lot from trying to help. It's probably easier for me to convey what's happened up until now.
Clive bought a sensorless 9FET KT controller from me a few weeks ago. No communication occurred at the time of purchase.
EDIT: My original statement was incorrect. Clive did get in touch before making a purchase, asking me to suggest a suitable replacement controller.
A week later, Clive got in touch to say that his KT880 LED display wouldn't stay switched on when connected to both his old controller, or the one purchased from me. I advised that the display was likely faulty and required replacement. Clive confirmed that the old controller worked while bypassing the display using the jumper plug from the new controller. I told Clive to keep the jumper plug and return the controller to me for a refund, which he did.
A few days later, Clive got in touch again to say that during a ride that afternoon, the bike had cut out and stopped working. I asked him to confirm with a DMM that he could see a feed from the 5V regulator - he couldn't, meaning the controller wasn't powered on. I asked him to check the voltage at the display to controller pass through and he reported 4V. I figured that the battery wasn't outputting sufficient voltage to initialise the controller, so asked Clive to check the voltage at the battery terminals and he tested 40V.
Clive continued to experiment and soon realised that although the battery was outputting 40V while open circuit, the voltage would fall to 4V when connected to the controller. The battery harness has been confirmed as okay up to the controller.
At this point, Clive asked if he could package up his kit minus the motor & battery and send it to me to test and replace parts, if necessary. When I received the kit (controller, display and throttle), I hooked it up to a bench supply and a diagnostic tester and was surprised to find that everything functioned as it should do. Although I didn't test the controller under load, I was happy with the output shown by the diagnostic tester, which displayed all phases firing in sync. The kit was then returned to Clive.
I am now of the opinion that Clive's issues are down to a faulty battery. At this point, I would usually test the battery under load, but Clive lives a couple of hundred miles from me, so not possible. At this point I advised him to take it to a local independent ebike shop who, might be willing to help him, which is where he is now.
