Transcoder not working

Hi all, I have been happily using plex without issue for some time, however, it has now decided that it can no longer play any movie/video files. (I have had “there was a problem playing this item” and transcoder unable to start messages) Music is fine. I have looked on forums and can discount disc space being the issue but I have no idea what or why this is happening. My server is based on an Open media vault system and I am not entirely sure where to get the relevant log files that may help identify a problem. from within the plex web app I got a log/debug file but am not convinced there is anything useful there except I did also notice that the log is recording all the events with a time one hour different to the actual time. I have checked the server and it displays the correct time so i do not know where this is going wrong or if it relevant to the transcoding issue.

Any and all help is greatly appreciated and sorry for my noobness.