Are there restrictions on Mp4 for HDS streaming

I am new to Adobe media player, so please bear with my ignorance.

I am able to HDS play some MP4 videos but for some others I get a 400 Bad request (from logs).

my player video src looks like http://<server>/hds-vod/somemedia.mp4.f4m.

Are there any restrictions how the MP4 file should be encoded or am I looking at the issue from the wrong side?

Cheers