Data format error. external table is no tin the expected format for (.xls file format)

ok let me try this way:
You posted a code that is importing data from CSV file:

let

    Source = SharePoint.Files("https://sharepoint.com/teams/", [ApiVersion = 15]),

    #"Filtered Rows" = Table.SelectRows(Source, each Text.Contains([Name], "Dashboard 2021 has completed") and [Extension] = ".csv"),

    #"Dashboard 2021 has completed csv_https://sharepoint com/teams/Report - Flow/Excel_file_Renamed/" = #"Filtered Rows"{[Name="Dashboard 2021 has completed.csv",#"Folder Path"="https://sharepoint.com/teams/Report - Flow/Excel_file_Renamed/"]}[Content],

    #"Imported CSV" = Csv.Document(#"Dashboard 2021 has completed csv_https:// sharepoint com/teams/Report - Flow/Excel_file_Renamed/",[Delimiter=";", Columns=44, Encoding=1252, QuoteStyle=QuoteStyle.None]),

    #"Changed Type" = Table.TransformColumnTypes(#"Imported CSV",{{"Column1", type text}, {"Column2", type text}, {"Column3", type text}, {"Column4", type text}, {"Column5", type text}, {"Column6", type text}, {"Column7", type text}, {"Column8", type text}, {"Column9", type text}, {"Column10", type text}, {"Column11", type text}, {"Column12", type text}, {"Column13", type text}, {"Column14", type text}, {"Column15", type text}, {"Column16", type text}, {"Column17", type text}, {"Column18", type text}, {"Column19", type text}, {"Column20", type text}, {"Column21", type text}, {"Column22", type text}, {"Column23", type text}, {"Column24", type text}, {"Column25", type text}, {"Column26", type text}, {"Column27", type text}, {"Column28", type text}, {"Column29", type text}, {"Column30", type text}, {"Column31", type text}, {"Column32", type text}, {"Column33", type text}, {"Column34", type text}, {"Column35", type text}, {"Column36", type text}, {"Column37", type text}, {"Column38", type text}, {"Column39", type text}, {"Column40", type text}, {"Column41", type text}, {"Column42", type text}, {"Column43", type text}, {"Column44", type text}})

in

    #"Changed Type"

This is Mcode, which means it can be found in 1 of 2 places:
1. Excel file
2. Power BI file

So if for any reason you need this refference in atnoher excel file, you can simply use Excel.Workbook(Folder.Files())
or excel workbook (sharepoint.files() ) 

also the formula CSV.Document do not have point to CSV files alone but to txt and XLS files also