Stacking multi-part movies

Hello,
I had multi-part movies (like Lord of the Rings: Return of the King) working perfectly but recently they do not. I had named each DVD file properly and put them in their own sub-folder. Plex would treat them as one continuous movie. Now Plex stops in the middle of the movie. Has anything changed?

I have seen Plex’s recommendation to combine the two files into one, but unfortunately the tool suggested on the forum will not install on my Linux Mint system.

Please show me exactly how you have the parts named for one of your problem movies.

What are you trying to install? Windows programs are useless on Linux.