Zach,
There are 2 LEDs on the HDLink. Which one is blinking? The one on the left of the USB port blinks when you’re connected via USB. The one on the right should only blink when it detects a 4:4:4 signal. If you have a valid SDI 4:2:2 signal going into the HDLink, the LED on the right should stay lit.
The message on that Final Cut Pro is providing is the worrying part though. It indicates that the hardware is not detected. You need to check your system profile to see if the card is being seen. You can also check the DeckLink preferences (in System Preferences) and see if it sees your card.
regards
Kristian Lam
Blackmagic Design