What are you trying to upload? A model? A place?
I've seen some errors people have where the size has been the problem, but that issue has been resolved.
If it's a model, try moving the model around and perhaps re-group it. Just for testing, you could also try to halve the size of it and see if both halves upload.
If it's a place, try copying all the contents of the place to a new place (Ctrl+N in Studio), and see if the new place uploads fine. |