How to run 4K files on a Oppo UPD 203?

I download 2160p MKV movie files and cannot seem to play them on my Oppo UPD-203. Do I need some type of interface or conversion piece to do this? Is the file size to large?They are in the 42GB range. Thanks!  Rick


90 percent of what I watch are concert videos. I assumed not many home theater members have experience with the Oppo 203.

The Home Theater section here is pretty inactive, but it would have in theory been the place to ask.  I would try a different site such as AV Forums.