Audio playback on mobile phones not working

A friend pointed out to me that he tried to play one of my tracks from Pond5 on his phone and it didn't work. I then tried using my phone and I had exactly the same problem. I tried other tracks from other artists and got the same result. This could be just an android issue (maybe it works on other mobile operating systems). Could this be made to work please? If clients click through our advertising portals to check out our music and they cannot listen to them on their mobile phones then that could potentially ruin our conversions. Many Thanks!

yes, i noticed the same on my android device