Strange surface current plot

Hi All,
I tried obtaining a surface current plot of my Vivaldi antenna in Ansys HFSS however, the current seems to be restricted to a small portion of the antenna (see picture attached). But in published papers, the surface currents are shown covering a good portion of the metallization boundary. I have tried increasing the port voltage (I am using a lump port excitation) from 1 volt to 10 volt still no difference. How do I obtain a correct surface current plot of the antenna? Kindly find the hfss file attached.

Thanks in anticipation.

How do you know it's not correct?

Select a log plot rather than a linear one, and adjust the scale accordingly.