I took a look at your account and see that you have a StudioLive 1602. What most likely has happened is that if you have upgraded to a new operating system such as Mac OS X 10.11, even if you have not upgraded to 10.11, if you are experiencing issues, the best solution is to uninstall and reinstall your drivers. We saw this when Yosemite (10.10) came out. Bottom line, to solve this you will need to uninstall your drivers and upgrade to the version that is supported for this new OS.
For Mac OS X 10.11, the older drivers for Universal Control 1.7.2 and older will not work. You MUST remove them and install the newer UC 1.7.3 driver.
To uninstall your drivers, please follow this tutorial:
http://answers.presonus.com/814/uninstall-reinstall-firestudio-studiolive-drivers-computer?show=814#q814, at the end of it a guide on where to find the latest driver and how to install them.
