...Good voltage at the terminals and the ground checks ok, just a blank display and no output....
There won't be any voltage at the output unless the EVSE is connected to a vehicle.
The CT500 is built like a tank. It is rated for 7.2KW and has a heavy duty cable and plug as well as options for network connectivity and for commercial, public, and exterior installations. Other than an early warranty replacement for excessive hum, mine has been otherwise faultless in daily use for more than five years. The CT in the model designation stands for Coulomb Technologies, now known as ChargePoint. If are not able to find parts or documentation searching ChargePoint, a search based on the original brand name might be more fruitful.
If you are inclined to debug and repair your unit, the installation guide at the below url which includes LED trouble messages might be helpful.
https://www.chargepoint.com/files/CT500-Installation-Guide.pdf
If you are not so inclined, you should be able to get good value for the case, cable and plug even if the internal electronics are not functional.
A third alternative might be to install one of the kits now on the market into the CT500 case. If you decide to consider this alternative I recommend that you consider only kits that carry a UL listing for the entire package and not just for the components.
Whichever path you decide to follow, keep in mind that the NEC and NFPA require that EVSEs be UL listed and that is not something you should want to debate with your insurance company following a fire event.
Please report back with what you decide to do and the end result.
Thank you and good luck.
KNS