This is a common error, but really easy to fix. It looks like this:
Two things need to be done before you can import the FCPXML file and continue with your workflow:
1. The original media file that you transcribed with Sonix needs to have the same name
If you renamed the original media file, please rename it back to its original filename. The FCPXML file tells Final Cut Pro to look for that exact filename.
2. The original media file that you transcribed with Sonix needs be in the same folder as the FCPXML file before you import it into Final Cut Pro
The FCPXML tells Final Cut Pro to look for the original file in the same directory as the FCPXML file. Please make sure that both files are in the same location and try again.
That's it! You should have everything ready to go.