This error typically means you haven't got enough space to accommodate the temporary files PluralEyes needs to create to work with your project.
PluralEyes needs about as much space to create temporary files as the project you've given it (ex. a 2GB project would need 2GB of space, 32GB project would need 32GB, etc.).
Head into the Preferences section of PluralEyes and adjust where the temporary files are stored to someplace with plenty of room for it work with.
If you are confident there should be enough space on your system for PluralEyes to work with, but you have it creating its temporary files on a remote or external drive, try adjusting it to someplace on your local drive (like your user library or desktop), and make sure your local drive has plenty of space, as sometimes there can be read/write limitations between your external/remote directories and programs like PluralEyes.
If that suggestion doesn't help: