Question

Mac Pro (Early 2008) El Capitan 10.11.6

2 x 2.8 GHz Quad-Core Intel Xeon

20 GB 800 MHz DDR2 FB-DIMM

Answer 1

Maybe there is a mismatch of versions (firmware/software). This is the latest and greatest:

Universal Control v1.8.3.40882 or v1.8.0.38751
Capture (Mac/PC) ­ 2.2.1.38751
RM Mixer Firmware ­ v9244
CS18 Firmware ­ v9203
AI Console Firmware ­ v9194

If you had Universal Control installed before, a complete uninstall might be needed. There is information about it in the knowledge base (http://support.presonus.com/hc/en-us/articles/210048113-How-do-I-Uninstall-Reinstall-my-device-drivers-for-the-StudioLive-AI-on-a-Mac-).