Hello. Thanks! I am on a iMac OS Sierra. The external harddrive icon is present on my desktop. All my other same make and model external harddrives pin to the dock. When I drag my new one to the right in the dock it just pops out. I even removed the others and re-dragged them in and they work fine. So the doc seems to be working fine - only this drive won't pin to the dock. However an alias of it will. I have formatted it just like the others. Any suggestions? Could it be a permissions issue? Or other? I'm at a loss. It's driving me nuts and there is nothing on google because it's a simple stupid thing that should work.