Hi Jules,
this is of course disabled. Otherwise you would be able to use e.g. 1000 demo versions to map entire NY and at the end of the day get the $99 version to re-export the city. That would not be fair to us.
We state this in the demo download panel, to avoid confunsion:
* Scenes created in RealityCapture demo cannot be loaded in paid instances of RealityCapture
We are really sorry that this happened to you. To avoid such situations, the most of other software disable save/export at all, but this is really a question what is better.