Unpivot only selected columns not working

This data is loaded via SQL 

let
Source = Sql.Databases("xxx"),

#"Pxxxxxx" = Source{[Name="xxxx"]}[Data],

#"dbo_'xxx$'" = #"xxxxxx"{[Schema="dbo",Item="'xxxxx$'"]}[Data],

#"Changed Type" = Table.TransformColumnTypes(#"dbo_'xxxx$'",{{"01/07/2017", type number}, {"01/08/2017", type number}, {"01/09/2017", type number},

{"01/10/2017", type number}, {"01/11/2017", type number}, {"01/12/2017", type number}, {"01/01/2018", type number}, {"01/02/2018", type number}, {"01/03/2018",

type number}, {"01/04/2018", type number}, {"01/05/2018", type number}, {"01/06/2018", type number}, {"01/07/2018", type number}, {"01/08/2018", type number},

{"01/09/2018", type number}, {"01/10/2018", type number}, {"01/11/2018", type number}, {"01/12/2018", type number}, {"01/01/2019", type number}, {"01/02/2019", type number},

{"01/03/2019", type number}, {"01/04/2019", type number}, {"01/05/2019", type number}, {"01/06/2019", type number}, {"01/07/2019", type number}, {"01/08/2019", type number},

{"01/09/2019", type number}, {"01/10/2019", type number}, {"01/11/2019", type number}, {"01/12/2019", type number}}),

#"Unpivoted Only Selected Columns" = Table.Unpivot(#"Changed Type", {"01/07/2017", "01/08/2017", "01/09/2017", "01/10/2017", "01/11/2017", "01/12/2017", "01/01/2018",

"01/02/2018", "01/03/2018", "01/04/2018", "01/05/2018", "01/06/2018", "01/07/2018", "01/08/2018", "01/09/2018", "01/10/2018", "01/11/2018", "01/12/2018", "01/01/2019", "01/02/2019",

"01/03/2019", "01/04/2019", "01/05/2019", "01/06/2019", "01/07/2019", "01/08/2019", "01/09/2019", "01/10/2019", "01/11/2019", "01/12/2019"}, "Attribute", "Value"),

#"Renamed Columns" = Table.RenameColumns(#"Unpivoted Only Selected Columns",{{"Attribute", "Dates"}, {"Value", " Values"}})
in
#"Renamed Columns"

I know how to do it, but I'm getting the following message when I try to close and apply

"The column 'first column' of the table wasn't found".