Streaming MP4

On my external drive connected to a Mac I have files that I converted with handbrake so that I could watch them through iTunes on my tv. I am know using Serviio and it reads all the files perfectly. However I have copied my collection to another drive to use with a pc and Serviio won't play any files converted using handbrake. All others are fine. Is there a solution to this or do I have to convert all the handbrake files to some thing else. Thanking all in advance.