Thanks for the logs and sample files. It appears that the MP4 file being produced by the latest version of PlayOn isn’t compliant with the specs and has errors which is throwing ffmpeg off when it tries to remux it from MP4 to TS for processing the file AND while trying to trim the start. During this process it’s losing some critical metadata about the video stream so it can’t be played back.
The short term solution is to enable the option to enable the option Skip remuxing files in the Conversion Task → Expert settings page to avoid having MCEBuddy remuxing the MP4 to TS and instead work directly on the MP4 files - which should avoid this issue.
The long term solution is to report it to PlayOn so they can fix it, as @scott_mb has tested that it’s working fine with PlayOn version 4.5