Two (multi) part videos will only play first part

[tom80H]

Keep in mind not all clients/players support stacked files (multi-file videos). Not 100% sure if the Fire TV client should be able to.
The safest way forward with multi-file videos is to append / merge them before adding them to Plex (e.g. using MKVToolNix).

[HowTo]: joining multi-part movies files with MKVtoolnix GUI

The purpose of this HowTo is to join videofiles, when a movie was ripped and split into two or more files. (This happens usually with very long movies [i.e. LOTR] or more often back in the day when we had Video CD or DIVX CDs) The ultimate goal is to have the movie back in one file, so there is no trouble in the various Plex clients which do not support multi-part files. The tool used is MKVtoolnixGUI it is freely available for all major PC operating systems. Therefore the container format …