This error occurs when your formula returns more than one value and Webi report doesn’t know how to aggregate those values. This error occurs in below ways:
Let us say an account number which is associated to more than one order numbers. Your solution will not work and hence you are seeing #MULTIVALUE “Multiple Order Numbers for the same account number”.
You can handle this by using an aggregated function as per your requirement like Max(),sum() or avg(). You can also check more details using this link: