Motu Audio Express issue

[TheDigitalMan]

Hi guys,

I'm new here: I just recently bought a new Motu Audio Express that I wanted to connect to my Macbook Pro mid 2012 via firewire 400/800.
After installing the latest software from the Motu website I sadly found out that the device was not able to connect to my computer via firewire for no reason. USB instead works alright.
I tried using the Audio Express via firewire with a Windows computer and it connects absolutely without a problem.

What could be the problem? My firewire port works fine when I connect (with the same cable) a small firewire HD. Could it be the OS? I'm currently running Yosemite 10.10.3 but also with Mavericks it wouldn't work. I also tried to reset PRAM as I looked over the forum and saw that it could be a possible solution but no avail.

Thank you very much for your help.

Greetings,
Stefano.