Hello Obi_Van_Kenobi,
To texture the imported mesh it is necessary to have the cameras aligned in the same coordinate space as the imported model is.
So basically you need to align the cameras first and then import the mesh. If it doesn't fit the scene, you can generate the rough model in PhotoScan, export it and bring the "good" model to the same position and dimensions as PhotoScan model, then import this modified mesh to PhotoScan and use Build Texture option from the Workflow menu.