On-site SQL data will not schedule refresh

Hi there

I have a Power BI Desktop file which only connect to our on site SQL servers and uses a combination of direct table and SQL query based Power Query sources. We have written M functions to return the names of the SQL server machines and databases as many of the sources are hosted on different SQL Server machines. These functions are then called in the SQL.Database M code to return the values required.

I have a personal gateway set up and all our other files are refreshing perfectly. No matter what I do, this data source will not schedule refresh. I have even removed the function calls and hard coded the connections to the SQL server but even this does not appear to make any difference

Thanks a lot