Unsupported data source in schedule refresh

Hi all...I am using a dynamic function to define and retrieve a site url (sharepoint list) to arrive at my data source.

Each row in my table refers to a sharepoint site so I first need to determine the site name and then read additional data from it to include in my table.

The root of the string is static and so is the list name but the actual URL differs depending on a specific parameter.

My function looks like this...

let LoadIssues = (SiteURL as text) =>

let
    Source = OData.Feed(SiteURL&"/_api/Web/Lists/getByTitle('Project%20Status%20List')/Items()?" )
in
    Source

in LoadIssues

I then invoke the query by adding a new column into my base table via 'invoke custom function'

I can then 'Expand' this column to see the fields from the list.

This all works perfectly in Desktop mode...bus as soon as I publish this to the web I am unable to refresh the data for the report, despite the face that it is drawing data from a data source (Sharepoint) that I have full permisions to access.

I just get the message "Unsupported data source in schedule refresh".

I this possible??? I can't find any answers online.

Thanks