Refresh issue with combined API and excel dataset

Hi All,

I'm using a dataset which is a combination of an Excel file (stored locally) and some API connections to a third party site. In the desktop app, I've joined these sources with a date table I created using the CALENDARAUTO() command to create the final tables, calculated columns and measures I've used for visualizations.

In the online service I've set up a data gateway connection to update the Excel file, set up the API credentials separately (as it says these are optional to add to the gateway) and set up the schedule refresh.

When I click refresh on the dataset, it seems successful (I get 'connection successful' messages in the refresh history) but when I go to the report online, the visualisations are not displaying the information correctly. Almost all data is displaying as 0.

I've tested the update separately for the excel file through the data gateway (it works) and the API connections without using the gateway (they work). When I do the refresh of the whole dataset within the desktop app it all works fine. 

I'm at a complete loss now, any ideas on what I'm doing wrong?

Thanks