I can't apply graph design because column isn't selected but it IS selected

Hello all! I'm trying to apply a graph design onto one of my columns, but everytime I try to do it I get an error message that says "Can't use the column design. One or more columns must be selected to set a column design" despite a column being selected. It works if I select the whole graph, but I only want it to apply to the one column. 

This is what I'm trying to do, starting at 8:07: https://www.youtube.com/watch?v=kS48XXS-LRM and attached is the error message despite the column being very much selected. Any help would be appreciated!