If your PC does not start after installing a new PSU, check the following:
• Make sure the PSU power switch is turned on
• Confirm the AC power cable is properly connected
• Check that the 24-pin motherboard cable is fully inserted
• Check that the CPU 8-pin power cable is connected
• Verify GPU power cables are properly installed
• Ensure all modular cables are connected correctly

If the issue continues, test the PSU with another system or contact technical support.