In order to use boxPlot(x,y) the number of elements in ‘x’ should be equal to the number of columns in ‘y’.
In your code y is of dimensions 9x9. boxPlot didn’t work because x is of dimension (1x24) and number of columns in y are 9.
‘y' is of dimensions 9x9 because tab2box(Xin,Yin) prepares data, in tabular form, for use in the BOX_PLOT function. Specifically, XIN and YIN are vectors (for example column vectors from a results table). Y is an N-by-P numeric array, where P is the number of unique elements in XIN, and N is the maximum number of occurrences of any individual element of XIN. In cases where elements in XIN do not occur an equal number of times, columns in YIN are padded with NaNs as per the documentation of the function.