Audacity worked fine until I updated my Macbook Pro with OS X 10.10.2. I see the tracks and try to record but no sound registers. Any suggestions from anyone who has had issues and has found a solution? Praying that Audacity is compatible with this new version… 
Audacity 2.0.6 and earlier are not officially compatible with Yosemite.
You can try the latest 2.1.0 pre-release from the top of http://www.audacity.homerow.net/index.php?dir=mac/&sort=date&order=desc. 2.1.0 should be released in a few days from now and officially supports Yosemite, but the Audacity version may not be relevant to your problem.
Please say exactly what you are trying to record (makes and model numbers of the equipment are good). If it is a USB or Firewire device, try selecting the device as input device in /Applications/Utilitites/Audio MIDI Setup and set the sample rate to the project rate you are intending to use in Audacity. Then restart Audacity and select the recording device you set up in Audio MIDI Setup in Device Toolbar.
Gale
Thank you for the update. To answer your question, I’m trying to record a voiceover using my laptop and/or a YETI mic. I did select the input, in the preferences/Sound area, which was indicated in the manual for the mic. Neither work, however, the laptop recordings were fine before I upgraded (on the advice of the head trainer at my local Apple store) who knew that I used my computer for voiceover work. 
Set Yeti for Cardioid pattern. Set Yeti input to mono (1 ch) in Audio MIDI Setup and choose the Yeti as recording device in Audacity’s Device Toolbar. Set Device Toolbar to 1 channel (mono) recording.
Otherwise you could take your computer back to the Apple Store and ask them to help you.
Gale