If there is a problem with importing a file, then PluralEyes will display an error message. If any clip in the project has an error when you start syncing, then PluralEyes will be prevented from syncing. So let's look at how to fix those errors!
To be able to synchronize your media files, PluralEyes “extracts” their audio content.
Successful. Clips from which audio content has been successfully extracted are displayed in the Media Pane with a thumbnail graphic. In the Timeline, the clip will show a waveform.
Failed. If audio extraction fails for a file, it is displayed in the Media Pane with an error message and possibly a question mark icon. In the Timeline, no waveform is shown for the file, and it is highlighted with a red border. In the Media Bin list, a bin containing media with errors will have a yellow warning badge.
Tooltip. If the clip failed, you can hover over the clip thumbnail in the Media Pane to view a tooltip with a description of the error.
Some problems are import errors, in which PluralEyes is making sure the file exists, and learning about the contents of the file. Others are media preparation errors related to the work that PluralEyes does to prepare for a sync and to make sure the audio can be heard during playback (sometimes called "conforming" the media).
"File not found"
If you import a project from an NLE or open an existing PluralEyes project, and some of the media cannot be found, you will be prompted to locate the media or to leave it "offline". This error message will only appear if you decided to leave the missing media offline.

"Unsupported format"
We recommend sending a problem report through the Help menu.
"Unable to read media metadata"
PluralEyes was unable to determine basic characteristics of the media, such as the type of media, video frame rate, and audio sample rate.
"Media unreadable"
We recommend sending a problem report through the Help menu.
"Duration unknown"
PluralEyes was unable to determine the duration (playing time) of the media. We recommend sending a problem report through the Help menu.
"No audio tracks found" or "No tracks found"
All media is expected to contain some audio. This error says that the media file did not contain any audio tracks. It shows when audio sampling rate or bit depth is modified through the AAF Export Settings. To fix the problem, in the Export Settings window, under Audio Details, make sure these options are both unchecked: Convert Audio Sample Rate To and Convert Audio Bit Depth To.
Keep in mind that some cameras record video without audio, or you may have transcoded the file and accidentally disabled the inclusion of audio. Those situations can also prompt this error message.

"Media error"
This error message shows when Consolidate Media was selected in the AAF Export Settings. To fix the problem, in the Export Settings window, choose Link to (Don’t Export) Media for both Video Details and Audio Details.

"Unable to create sync temp folder"
PluralEyes creates folders for its temporary files, usually alongside the media and imported NLE project. If it is unable to create a sync temp folder, it will prompt you for an alternative location.
"Audio levelling failed"
We recommend sending a problem report through the Help menu.
"Audio extraction failed"
We recommend sending a problem report through the Help menu.
"Audio extraction stalled"
The extraction operation timed out; the users computer may be too busy doing other things and/or low on free memory.
"Transcoding failed"
We recommend sending a problem report through the Help menu.
"Unsupported codec"
We recommend sending a problem report through the Help menu.