Okay. I didn't realize there were 2 different BlendSwap files — I had the BY-CC, so I downloaded the the CC-0.

Upon opening both pluginFurniturecatalog.properties files, I noticed that the CC-0 was an older file (copyright 2016 but perhaps last modified in July 2019), whereas my BY-CC was created August 2020 by FLE. There's quite a difference in the file headers.

However in both files there is a corresponding category #x for each furniture entry, which FLE should change once you save the file after editing.

So what I need for you to do now is open the MODIFIED CC - 0 properties file and tell me what you see at the top of that text file.
Also, did you extract either SH3F folders from the zip archive into the furniture folder?