I have updated my WD TV Live Plus and I started to get message “Unable to play this file format…”, when I play my MP4 video. It used to work fine in a version before 1.04.10
Do the old “reset to factory settings” trick and unplug for a few minutes.
If resetting to factory settings does not help, please post the media info here for the file(s) that won’t play.
Mediainfo(freeware) - after downloading and installing the program, right click on the video file and select mediainfo, then paste the info here.
If it doesn’t help, delete the hidden folder “.wd_tv” on every usb drive you use together with your WDTV.
Sometimes files can become corrupt for some reason (e.g. if you unplug the power cable while your usb drive writes/reads data), so it makes also sense if you check with your pc the surface of your usb drive(s).