Getting Excel file content from different SharePoint sites

Hi,

I have several SharePoint sites that have an identically named folder which contains a Excel file. I would need to go through a list of site URL's, get the files and append these files into one table.

I have a separate SP list with all site URL's which I filter to get the list of URLs I want.

I also made a custom function which gets the Excel file from the correct folder given an URL as a parameter:

(URL as text) as table =>
let
    Source = SharePoint.Files(URL, [ApiVersion = 15]),
    #"Filtered Rows" = Table.SelectRows(Source, each ([Folder Path] = URL&"/powerbi/")),
    #"Filtered Hidden Files1" = Table.SelectRows(#"Filtered Rows", each [Attributes]?[Hidden]? <> true),
    #"Removed Columns" = Table.RemoveColumns(#"Filtered Hidden Files1",{"Extension", "Date accessed", "Date modified", "Date created", "Attributes"})
in
    #"Removed Columns"

I am able to get the content as binary into my table by invoking the function but when I try to 'Combine Files' it gives me an error on Formula.Firewall.

Url list

Invoked function to get contentError on combining

I went through a couple of threads with similar issues and read through Ken Puls' blog, but I can't get my head around on how to fix the issue. 

Any help on this issue?

Thanks in advance!

Br,

T