DM_GWPipeline_Gateway_MashupDataAccessError indicates an issue with data access in the gateway used by your Power BI mashup. UnderlyingErrorCode -2147467259: This specific code points to a "Remote procedure call (RPC) failed" error, suggesting a connection problem with the Bing Maps API.
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Ensure your Power BI gateway can access external websites like Bing Maps. Check if any firewalls are blocking the connection. Review your Bing Maps API key in Power BI settings. Ensure it's valid and hasn't expired. top and restart the Power BI gateway service on the machine hosting it. In Power BI Desktop, right-click your Bing Maps data source and choose "Refresh."