I just got a Dell UZ2215H and attached it to my mac mini with an HDMI cable. The built-in microphone wasn't working and when I touched the mic button on the bottom of the screen to see if it was muted, the screen displayed something to the effect of "no USB cable". I thought I didn't need to attach a USB mic if there was one built in. I can't figure out how to get the built in mic to work. Anyone have any suggestions? The manual was completely unhelpful as was a google search and support from Dell for mac. Thank you.