avrdude: stk500_recv(): programmer is not responding - OSX10.11
Has this ever worked?
Can you use avrdude and hit the target?
There is a terminal mode in avrdude you can also use.  At least this would help you determine what is working.  

Sounds like a configuration issue.  If you have the ability to 'follow the tail' (tail -f ) I'm assuming that you have 'like' tools we have in Linux like lsusb to assist?

You can ensure yourself that if it says it isn't found, it's not finding it, so it's not wherever it's looking. :)