Matrix_ Help

in order to do that the rows & column items have to be in rows in the table

you can achieve that in 2 ways:

1) unpivoting your original table in query editor, e.g. like this

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("ddBLCoUwDAXQvWSs0KT1N9T3/LuD4v63obF6Rw2UQMMhNyRG6qkgcdyWju93f+pGi3YDnUWkAUASYPGo4hP6AfmEfKUdfsbwQ/4g4SVBzVeUjCCVNWUCqfPrzgCNve4C1FpBK0iXD9o+wM4O2oHYCjpAJHuX8wI=", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type text) meta [Serialized.Text = true]) in type table [Client = _t, Month = _t, #"Total Charge" = _t, #"Total Payment" = _t, #"Total Balance" = _t]),
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"Client", type text}, {"Month", type date}, {"Total Charge", Int64.Type}, {"Total Payment", Int64.Type}, {"Total Balance", Int64.Type}}),
    #"Unpivoted Columns" = Table.UnpivotOtherColumns(#"Changed Type", {"Client", "Month"}, "Total", "Value")
in
    #"Unpivoted Columns"

then you have one measure which is just 

Measure= SUM(Table[Value])

2) create a new table with a row for each column you wanna sum

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WCskvScxRcM5ILEpPVYrVgQkEJFbmpuaVIIk4JeYk5iUD1cQCAA==", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type text) meta [Serialized.Text = true]) in type table [Total = _t]),
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"Total", type text}})
in
    #"Changed Type"

and then use this measure

Measure 2 = 
SWITCH(
 SELECTEDVALUE(RowsTable[Total]),
 "Total Balance", SUM('Table'[Total Balance]),
 "Total Charge", SUM('Table'[Total Charge]),
 "Total Payment", SUM('Table'[Total Payment]),
 BLANK()
)