Mixing Stacked Bar chart and Line Chart

Good Morning,

I am looking for a little advice on the below.

I have created a mixture of a stacked and standard bar chart showing different months of different years.

The final year - 2014 - needs to be represented as a line, the data is already included as I have included this as a bar to start with.

Basically when I click on the 2014 data to Change Chart Type, the bar disappears but is not replaced with a line - it just disappears completely.

Does anyone have any idea what I am doing wrong?

Many Thanks for any help :-)

L