"I have an audio file that only plays sound from the left channel, which means I'm hearing nothing from my right speaker. Is there any way to fix this?"
If you're only getting audio from the left channel of an audio file, that means whoever saved the file stored blank information on the right channel. You can fix the file so that it plays across both the left and right channels, but you won't be able to create a true stereo experience isolating portions of the audio in either the left or right channel the way a commercial audio CD might. To fix the file, you'll need download some audio conversion software.
There are several audio converter applications capable of fixing your audio file. The one I find easiest to use for this purpose is Switch, because it exposes the necessary conversion features in a very simple way (and it's also free for most uses).
Before you begin you need to download Switch Audio Converter and install it. It works with both Windows and Mac, making it a fairly universal solution. Once you have Switch Audio Converter installed, launch the application.
Add your file to Switch then choose the encoder settings.
For MP3 output, choose Constant Bitrate option. In the Other section of MP3 Encoder Settings you need to select the Channel Encoding Mode: Mono. Joint Stereo, which is a stereo compression that combines both the left and right channels to reduce the amount of data stored in the file, might also work, but I found this to be an unreliable option with each audio converter I tried except for Adobe Audition (which is my favorite audio editing app, but an expensive solution for addressing this particular problem). Once you've made those configuration changes, click Convert and Switch will create a new file that fixes your left channel only problem.
