Flag based on all data in the table

Anonymous , Please try this power query code

let
Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WMjAwcHRU0lEyVIrVAfOcnYE8YxQeXM7NDVnOyQlZzsUFQ6WRUmwsAA==", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [CustomerID = _t, ProductID = _t]),
#"Changed Type" = Table.TransformColumnTypes(Source,{{"CustomerID", type text}, {"ProductID", Int64.Type}}),
#"Added Custom" = Table.AddColumn(#"Changed Type", "Cnt", each 1),
#"Pivoted Column" = Table.Pivot(Table.TransformColumnTypes(#"Added Custom", {{"ProductID", type text}}, "en-US"), List.Distinct(Table.TransformColumnTypes(#"Added Custom", {{"ProductID", type text}}, "en-US")[ProductID]), "ProductID", "Cnt", List.Max),
#"Changed Type1" = Table.TransformColumnTypes(#"Pivoted Column",{{"1", type text}, {"3", type text}, {"2", type text}}),
#"Replaced Value" = Table.ReplaceValue(#"Changed Type1","1","Y",Replacer.ReplaceText,{"1", "3", "2"}),
#"Replaced Value1" = Table.ReplaceValue(#"Replaced Value",null,"N",Replacer.ReplaceValue,{"1", "3", "2"})
in
#"Replaced Value1"