My external hard drive stopped working after OS X 10.11 update. I contacted support and they were not able to help. I have tried resetting the SMC and that hasn't helped. Restarting makes no difference. The problem is with the OS I suspect and APPPLE could care less about the fact they have screwed up. Other people are reporting USB issues since the update - Apple needs to fix this. However, if any of you have found a quick fix I would love to hear from you. Thanks.