Mackie Onyx 820i - FireWire Bus Issue

I recently purchased a brand new Mackie Onyx 820i with serial number beginning with 204 off of eBay. I'm running OS 10.9.5 on a 2009 iMac and I have installed the Mackie 4.2 driver and per the web site everything should be compatible.

However, when I launch the Onyx-i Control software I get a msg saying no devices connected. Also, when I go into the system report under the FireWire Bus I see a msg "Warning: Unable to list FireWire devices."

I've tried different cords, shut down and restarted with everything unplugged and still not luck. I tool my iMac to the local apple repair and they plugged in an external hard drive via firewire and it recognized it right away. They couldn't find anything else wrong except I need to replace the hard drive fan.

I called Mackie and they were no help since they just confirmed I had the latest driver and that I tried uninstalling and re-installing. I've tried a few other items I have found on these boards but nothing seems to be working. Really appreciate some additional thoughts/guidance on how I could solve or even diagnose the issue further.

Thanks,

JP