I have used Audacity for some time in the past with no problems. I downloaded the new Audacity on my Mac with Yosemite. The program loads, but I have no project window. I deleted the .cfg file as has been suggested…nothing happened.
Can you post a picture of what you see when Audacity opens without a project window.? How to take a screenshot on your Mac - Apple Support.
If there is an Audacity menu bar at the top of the Audacity screen, try clicking File > New in that bar.
Make sure you obtained Audacity from the link given in the pink panel at the top of this page.
Gale
Unbelievable…I did the download yesterday as you said…I tried for two hours to get something to work. I just got your response, opened Audacity to get a screenshot, and the recorder is there! Thanks for the good thoughts. 
I am getting the impression Audacity opened (the menu bar said “Audacity”) but something you were expecting was not there. Was it the red Record button?
Were you trying to import an audio file and the blue waves did not appear?
Please do post a screenshot if it happens again.
Gale