I have a 2010 macbook pro running the latest version of Sierra. It has just begun to not respond to the sleep timing in system preferences, keyboard command for sleep or to selecting the apple symbol and then selecting sleep. If you close the lid it will go into sleep mode. I have done a clean install of Sierra however after a few hours it begins to have this response. I am running the existing 320 HDD from the initial build of the machine and it is running well except for this problem. I would appreciate any suggestions as how to overcome this problem. Seems that activity monitor shows something that is stopping my mac from sleeping (hidd files) whatever they are. I have 2 firewire backup drives attached and a mac mouse nothing else. Any suggestions on what may be the problem?