If your Raspberry Pi does not boot with the included power supply but with a USB-C cable which is plugged directly into the raspberry, try the following:
The two pins of the power supply do not make constant contact with the part of the plug that you have to screw on. Put a little solder on the pins of the PSU to increase the pressure:
The result should look like this:
Screwing on the plug should be more difficult afterwards but not feel like you are breaking something.
This also applies if your multimeter displays a voltage (this was the case for me). The weak connection supplies some current, enough to measure it, but not enough to power the EON.
If you are not sure if this is the fault you are having, plug in the power brick for a few hours without anything attached and then remove the screw on plug. The pins should smell a little burned and the metal contacts on the plug side should have black spots where the pins touch it. This is an indication of this problem.