After upgrading to Yosemite you will need to uninstall Universal Control and then reinstall version 1.7.2. Your FireStudio interface should be working after doing this.
Please follow our knowledge base guide on uninstalling and re-installing your FireStudio files/drivers:
- FireStudio Project
- FireStudio Mobile
- FireStudio Tube
- FireStudio Lightpipe
Note: The Firestudio (26x26) is not supported on OS X 10.8 or higher.