Important note: PLY format is a container and it can contain different types of data: 3d mesh, Points Cloud or Gaussian Splatting. Make sure you have exported Gaussian Splatting.
Now go to the Properties panel.
Unroll Model 1 tab and click on browse button in 1 Model section. And choose your Gaussian Splatting model (gs_model.ply)
Depending on the size of the model it can take a few seconds to prepare a model to work with your project. After the process is done you can see your model in the scene.