It would help us if you could provide the necessary information requested in the pink panel at the top of the page.
Have you installed Audacity correctly so that you are not running Audacity directly from the DMG?
Did you export the recording as WAV or AIFF, import that file and it is that imported file that has no waves? If so, did you move, delete or rename the file?
Or did you save an Audacity project containing your recording and that project has no waves?
If none of that describes the issue, you may have problems writing to your hard drive. Please open Help > Show Log… and post what it says inside there. If necessary you can drag in the Log window from top to bottom, COMMAND + C to copy, then paste here.
Gale