There have been a number of issues, it seems, with the Play Movie event command. Either they’re not playing or they’re not showing up in the event list, even though they’re in the movies folder. There IS no import function in RMMV, as there was in previous RPG Makers, so you now have to manually copy and paste "assets" (resources) into their respective project folders.
No Movies in RMMV Play Movie Event
The problem as I see it is that since RMMV supports much higher resolutions and can be used on multiple platforms, faster, higher quality graphics and sounds are almost certainly more of a requirement. Older formats are quickly becoming incompatible. So as a result, this leads to a bit of fickle behaviour.
It’s now no longer a matter of importing (or in RMMV’s case copying and pasting) movie files into the movies folder and expecting them to work.
RMXP and RMVX didn’t support videos natively, but there were various scripts that would allow you to play movies; these were often unreliable depending on how the video was saved, in what format and whether additional codecs were required.
RMVXA, however, did have solid support for movies using OGV (developed byXiph.org Foundation), which is basically a highly-compressed video file format to vastly reduce HD movie sizes.
With RMMV, MP4s must be encoded with the H.264 codec for them to work properly, it seems, and placing an MP4 into the movies folder alone will no longer work! Nor will they show up in the Play Movie playlist.
Movies in Events Playlist
This might be partially due to its support for multiple platforms, including HTML5, so something else is required for more cross-compatibility.
As a result, RMMV can also accept the HTML5 WebM Movie (.webm) file format.
For conversions I’d highly recommend downloading Any Video Converter, as it does support both formats (and many others) required by RMMV.
Once converted, when you copy and paste the webm movie into the movie folder, videos will now play and show up in the event command’s playlist. In fact, according to RMMV’s help file:
The file formats that are playable depend on the operating environment, so please prepare the below 2 file formats with the same file name.
MP4 (.mp4 encoded with H.264 codec)
* When creating a game that will be played on Windows or Mac, please prepare only the WebM file format. When creating a game that will be released on the web or made for Android/iOS, both file formats are required.
That is something I overlooked until I read the entire help file (yes, I did that!). During development, then, as mentioned, movies will show up and play only if the .webm video format is used. However, the MP4 file should also be included if games are developed for websites, Android or iOS.
It really does help to read help files! (This might seem blatantly obvious and a bit condescending, but I rarely actually read the help files, except when I need them, and I know may people who don’t either.)