Wdtv live plus doesnt detect media on WD My passport 1TB hard drive

I recently purchased a WD My passport 1TB hard drive. I hooked it up to my WDTV plus via usb and it can not find the media on it. I had an MP4 and MKV file on it. Any ideas what the problem could be? I updated the wdtv plus to the latest firmware but it didnt help.

What filesystem? ExFAT won’t work for example.

ok I feel stupid. The wd passport wasnt formated for windows yet because it was formated for a mac when I bought it.  I recently installed an internal hard drive and was copying the video files to that on accident. Iam currently formating the wd passport and will try it again.  Thanks for the reply.