Can you try downloading this sample MTV video here? -->
Sample Video: MTV format for 1.8" screen player. See if that works on your player or not.
Do you have a SAMPLE video on your player as well? If you do, can you upload it somewhere and post a link so we can download it and have a look?
Also, try installing this tool here -->
MTV Video Converter 1.12.11.3.
Let us know.