I have a mac mini and have just upgraded to Mac OS Sierra.
Once I did that, any time I tried to open Audacity, I get a message which says:
Audacity is already running
The system has detected that another copy of Audacity is running.
Running two copies of Audacity simultaneously may
data loss or cause your system to crash.
Use the New or Open commands in the currently
process to open multiple projects simultaneously.
Problem is, I cannot find another copy of Audacity on my home screen running. I even trashed all the old audacity app and uploaded the most current copy ONCE and am still getting the message.