plotting – Cannot divide a list of numbers by their total from uploaded data

I have a list of numbers in a CSV file which my code uploads to Mathematica. I upload the file, then flatten the list and sort it to arrange the numbers in ascending order.

After doing that, I would like to divide each number in the rearranged list by the total of the list and then plot it. I am using the code shown below, but it says it is ‘not a list of numbers or pair of numbers’. What am I doing wrong? What do I need to change?

Thanks,
Sid

FormPage[{"data" -> "CSV"},
 a = NumericalSort[Flatten[#data]] &;
 b = a/Total[a] &;
 ListPlot[b]
 ]