If you are facing problems in viewing your 3D model in Oculus Go or Samsung Gear VR, follow these recommendations:
We recommend your model size to be less than 50MB and less than 250.000 polygons. If that is not the case, I suggest you take a look at our article to optimise models for optimum loading in VR HERE.
Since the trial plan supports 1 model only, in order to try the feature for multiple models - you need to delete the existing model from the web account and re-upload from the plugin. You can see how to delete an existing model HERE.