The reason this isn't working is because you haven't built your source data properly for the anchoring.
Remember, Tableau cannot natively build this so, we must create the base in which Tableau can plot what we tell Tableau to plot, where we tell Tableau to plot it so the source needs to follow the number 1 rule in order for this to work.
See my dashboard here for further notes and open the attached data-source so you can see exactly how to set-up your source: Superstore Waterfall
The basics of it are:
Inset a new line into your source data with every field nulled with exception of the [Waterfall] field, this must have a value of 'Start' on the nulled entry, with all remaining fields valued to 'End' <<< this is the key, without this, nothing will work