It plots a horizontal dotted line at 55 from 0 to 7.
If it works independently, then there are several possibilities, some of which are that the plot limits are such that it is there, however is either too short to be seen clearly, or outside of the plot limits (xlim, ylim) entirely, or is being overplotted by something else.
One option would be to plot it temporarily as:
plot([0 7],[meet4060 meet4060],':k', 'LineWidth'10)
to see if it becomes visible.
We would need to see relevant parts of the current code to be certain.