When you create a new scene, you have an empty timeline. Unless you are assembling from an EDL or importing a Wiretap timeline, you must manually create a new cut.
The Save button is for saving editorial changes to a currently loaded cut.
If you want to create a new cut, you will need to click New.
To create a new cut:
A new cut is created. The name given to the cut appears in the Cut Name list.
To create a new cut version or to save a cut with a new name:
A new cut is created from the current timeline. The new name given to the cut appears in the Cut Name list.