Error creating a lookupvalue from a DAX table

Hello Community,

I am trying to lookupvalue from one table into another table both Tables were created with using Summarizecolumns  function as shown below.

And the reason I am using the Summarizecolumns is that they make my model run faster.

The data used  to mimic my scenario  is avaiable on this link -> https://community.tableau.com/s/question/0D54T00000CWeX8SAL/sample-superstore-sales-excelxls 

Table1

Table1 = SUMMARIZECOLUMNS(
                  Orders[Customer ID],
                  Orders[Category],
                  Orders[City],
                  Orders[Country],
                  Orders[Order ID],
                  "Sum of discount",sum(Orders[Discount])
            )

Table2

Segmenttable = SUMMARIZECOLUMNS(
                 Orders[Customer ID],
                 Orders[Country],
                 Orders[City],
                 "Sum of Sales",SUM(Orders[Sales])
)

Lookupvalue query

LOOKUPVALUE('Table'[Sum of discount],'Table'[Customer ID],Segmenttable[Customer ID])

I get this error

A table of mutiple values was supplied where single value was expected.

I humbly appreciate ideas to resolve this issue.

Thank you.