As the other commenters have said, it will be difficult to know for certain what's going wrong until we see the actual data frame you used to make the plot. Two things for now:
First, are the values of SH all integers? Note that every one of the boxplot statistics is an integer value: 0, 2, 4, 5, 9 and 11. This seems unlikely unless SH is all integer values.
Second, the midline of the boxplot is the median, rather than the mean. If SH is all integers, the median will likely be an integer. Is it possible that the median of SH is always 2 for the particular combinations of PPGENDER and INDUSTRY_col in your graph?