PBI - all data loaded are null

Hi

I have loaded data from folder consisting 4 excel files. The column titles are the same. After several changes, except for sample file, the others showed null when loading to PBI.

let
Source = Folder.Files("Shared folder\Data analysis\Speaker Data\Data to PBI"),
#"Filtered Hidden Files1" = Table.SelectRows(Source, each [Attributes]?[Hidden]? <> true),
#"Invoke Custom Function1" = Table.AddColumn(#"Filtered Hidden Files1", "Transform File", each #"Transform File"([Content])),
#"Renamed Columns1" = Table.RenameColumns(#"Invoke Custom Function1", {"Name", "Source.Name"}),
#"Removed Other Columns1" = Table.SelectColumns(#"Renamed Columns1", {"Source.Name", "Transform File"}),
#"Expanded Table Column1" = Table.ExpandTableColumn(#"Removed Other Columns1", "Transform File", Table.ColumnNames(#"Transform File"(#"Sample File"))),
#"Promoted Headers" = Table.PromoteHeaders(#"Expanded Table Column1", [PromoteAllScalars=true]),
#"Renamed Columns" = Table.RenameColumns(#"Promoted Headers",{{"Speaker data 2021.xlsx", "Source.Name"}}),
#"Changed Type" = Table.TransformColumnTypes(#"Renamed Columns",{{"Source.Name", type text}, {"No", Int64.Type}, {"Datekey", Int64.Type}...
in
#"Changed Type"

When I create a new PBI file from the same folder, evertything are good.

Anyone please can help? Thanks a lot.