Plugboard worked on everything except one series

[squadz]

I just did plugboard for the first time ({series}{series_index:0>2s| – | – }{title})

Any format/any device for the other settings.

It worked on my entire library, except for one single series.

Here's the metadata of one of the books in the series that aren't working: https://imgur.com/a/hXjTKzu

Here's the metadata of one of the books in another series that does work: https://imgur.com/LcX7cOa

For the one that doesn't work, it just shows the title on my Kindle Paperwhite. Not the series - 01 - title like the others do.

Anything that I'm missing here?