Commonly you can't turn a PXIe chassis ON without an embedded controller, the switch on an NI PXIe chassis is a software switch, unlike a hardware latch on previous PXI systems. This is the reason why you do not actually hear the power button when you press it to turn it on. With a software switch, the chassis will not power on unless there is a controller in the chassis.
You can turn ON/OFF your PXIe chassis if it has an Inhibit Switch in the rear panel. You need to move the switch from Default position to Manual Mode to bypass the controller and enable the power supply. Then you can power ON the chassis. If you want to power off the chassis, you can use the Inhibit signal (active low) on pin 5 (see image below) of the Remote Inhibit and Voltage Monitoring connector to power off the chassis.
You can check the article below to verify if your PXIe chassis supports the Inhibit modes. Remote Inhibit, Voltage/Fault Monitoring, and Remote System Monitoring on PXI Chassis