I would test the Power Supply by disconnecting the Supply leads from the 3D Printer an measure the voltage.

Reconnect and measure the voltage at the Power Supply and the controller if there is a voltage difference you may need the make the Supply leads larger gauge wire.
You can then measure the voltage on the controller while trying to heat the hot-bed or hot-end one at a time, if everything look then heat both an measure again.

Testing can be a long winded process to see if the supply is damaged and cannot supply the full power.

If you cannot get a full 12 or 24Volt with no load connected then the testing is done an the supply may be damaged.
This process means you need to be able to use a volt meter.

Have any questions post.