Media Encoder "not currently encoding"

I am running the trial version of Media Encoder CC and have no prior experience of this sort of software (apologies for limited knowledge and I hope this mean my question has an easy answer!). I experimented by trying to convert some m2ts files to mp4 using the default presets chosen for me. The first conversion worked fine then, when I tried a small batch (or any single file since), I get a "not currently encoding" message. I have no idea why.

Any help in rectifying would be much appreciated?

Maurice