Applies to: Saffire Pro Range
If the 'Power' and 'LKD' LEDs on your Saffire light when it's connected by not the 'FW' light, it suggests the device is powering on but not making a connection to your computer via Firewire.
If the 'LKD' LED on your Saffire is not lit, you should ensure you have installed the latest version of Saffire Mix Control for your system from https://focusrite.com/downloads .
If that does not help, it's possible that either the Firewire cable or your Firewire card are not working correctly and so you should try testing another Firewire cable and testing that other Firewire devices are working with your computer.