I have a D200 and a D7000. The D200 triggers the SB600 in Commander Mode without any issues. The D7000 on the other hand will not trigger the SB600 with absolutely identical settings in Commander Mode to the D200's. Am I missing some secret/hidden setting? All channels/groups are identical.
Some things to check:
- Make sure custom setting e3, Flash cntrl for built-in flash (Menu > Custom Settings Menu > Bracketing/Flash > e3) is set to CMD↯
- Under setting e3, Group A should be set to TTL or M. The SB-600 doesn't have a thyristor sensor, so A won't work.
- Make sure your compensation or power isn't set so low that you can't see much light.
- Under setting e3, set Channel to 1.
- The SB-600 should be in slave mode. Hold Zoom and - until the menu appears, and press + or - until the synchronization icon (squiggly right arrow) appears press Mode until this turns to On.
- Make sure your camera is in P, S, A, or M -- CLS doesn't work in Auto or Scene.
- Make sure you have line of sight from the D7000's on-camera flash to the IR sensor on the SB-600.
- Is the D7000's flash firing?
Oh, and one thing that I find really annoying that might be tripping you up: Make sure to hit OK after changing settings in the Commander Mode menu -- just changing them without hitting OK won't save them.
I had a similar problem with a SB-600, so I borrowed an SB-700 and found the problem continued with that flash. I set them up to both run on the same channel and found they would fire / not fire at the same times, so I knew it had something to do with the camera. When I turned my built in flash from TTL to "--" everything started working fine. I don't know why, but the TTL flash of the built in flash was interfering in some way. I even found that I could leave it in TTL and cover the built in flash with my hand and the other flashed would then fire consistently. Weird, but glad I found a way to make it work.