The log file as a batch file for debugging
When nothing appears to be happening, even after you have done a Metadata > Read Metadata, it is often because Exiftool has been enable to process the images.
To help you find out what has happened, the plugin can generate a log file which you can edit and use to run Exiftool in its interactive mode which displays messages about its activity and any problems it encountered.
In Windows, I change the log file's extension to .bat, and it will then run as a batch file. On Mac I prefer to cut and paste into a Terminal window.