Apple Remote Desktop not working on Sierra
Pascal a.k.a. xvi answered this question about ARD not working on OS X Sierra.
My macs with OS X Sierra have the symptom of ARD not working sometimes and other times ARD starts up just fine. Here is the fix that worked for me:
https://discussions.apple.com/thread/7733349

Apple Remote Desktop doesn't start after sierra update. We tried with same problems on different client (macbook pro, imac and mac pro)

The workaround I have found is this (requires to be administrator):

Launch Terminal, then type:

 sudo pkill -u -2 ARDAgent


and type your password as requested.
Then, Remote Desktop.app will launch (or, if launched and hung, its main window will appear).