Why can't I upload a new Excel spreadsheet to the model?

First, you will want to check that you are the owner of the model. The owner will be displayed in the upper righthand corner of the Visualizer under "Copy" and "Delete". Contact the owner or a Visualize specialist to help with this.

Another possible reason for not being able to upload an Excel spreadsheet would be: not being in a development version. 

If you only see blue headers labeled "Production" you will want to create a new development version

Click "+ Create New Version" at the bottom of the most recent Production section.

Select the type of version you want to create (typically a New Revision Version will be most appropriate).

Once you see the green header labeled "Development" you should see the link to "Create Model from Spreadsheet"