I am waiting for the update of this script.
It is presumed that Apple has changed something.
Mp3tag v3.13 also didn't work, so I updated to 3.14 and tried again, but it still doesn't work.
In the end, it seems that the script needs to be updated.
I've used it well so far, and I'll be grateful for it in the future.
I'm not good at English, so I'm using a translator, so please forgive the awkward sentences.