FBReader doesn't open PDF files even with the plug-in installed

[ArGoSh]

I've been using FBReader to open a bunch of e-pub files flawlessly but then I give it a try to its PDF capabilities so I installed the PDF plug-in. It got installed and recognized by the main app with no issues (doesn't appear in the plug-ins options and Android shows the installed app perfectly) but it doesn't open any PDF file; it opens FBReader but does not load the PDF.

I tried to browse files from different locations (download, SDCard...) getting the same results (open the PDF with the app and directly from the android file explorer).

Also, I tried to look in the source code but as I said in #5 (comment) I didn't found it available :S.

PS. I'm running Android OS 7.1.2 (Nougat).