Check you have a spare power cable

In order to get all devices to work correctly on your USB 3.0 card, it's a good idea to plug in the optional power.

Molex or Floppy?

 

pci card power connector
Some cards require power from a Molex connector

Computer power supplies normally have extra connectors in case you ever need to upgrade your computer.

In order to deliver enough power to a USB 3.0 PCI and PCIe card you will need to plug in a spare power connector from your computer power supply. Some USB 3.0 PCI and PCIe cards require a Molex power connector or a floppy power connector.

No spare power connector on your computer power supply?

A Molex power splitter plugs into one that is already in use and splits the connection into two.

Molex Floppy connectors
Floppy vs Molex connectors

No floppy power connector on your computer power supply?

You can use this convertor to change the Molex connector to a 4 pin floppy power connector.

Does your computer power supply only have sata power connectors?

You can use this converter to change the Sata connector to a Molex connector.

You can use this converter to change the Sata connector to a Floppy connector.