What causes MashupException.Error?

The on-premises data gateway cannot reach the Dataflow Gen2 staging Lakehouse on port 1433 (TDS protocol). Firewall rules on the gateway server or proxy servers block outbound traffic to Fabric staging Lakehouse endpoints on port 1433. Multiple queries in the dataflow reference each other — the dataflow engine must read staged data via TDS (port 1433) before writing the next query. Note: dataflow writing to a Lakehouse uses HTTPS (port 443), but reading staged data between queries requires TCP port 1433

How do I fix MashupException.Error?

Check the error detail for the failed activity 'WriteToDatabaseTableFrom_...' — confirm it is a TCP/port 1433 connectivity issue.. Update firewall rules on the gateway server to allow outbound TCP port 1433 to these endpoints: *.datawarehouse.pbidedicated.windows.net, *.datawarehouse.fabric.microsoft.com, *.dfs.fabric.microsoft.com.. To scope to a specific workspace, navigate to Fabric workspace → DataflowsStagingLakehouse → View Details and copy the SQL connection string.. Workaround (if firewall cannot be changed): combine referencing queries into a single query.. Work around the error by disabling staging on all referenced queries in the dataflow.

High severitygateway

Power BI Refresh Error:
MashupException.Error

What does this error mean?

The Power Query Mashup engine failed. In Dataflow Gen2, usually caused by port 1433 being blocked to the Fabric staging Lakehouse TDS endpoint.

Common causes

1The on-premises data gateway cannot reach the Dataflow Gen2 staging Lakehouse on port 1433 (TDS protocol)
2Firewall rules on the gateway server or proxy servers block outbound traffic to Fabric staging Lakehouse endpoints on port 1433
3Multiple queries in the dataflow reference each other — the dataflow engine must read staged data via TDS (port 1433) before writing the next query
4Note: dataflow writing to a Lakehouse uses HTTPS (port 443), but reading staged data between queries requires TCP port 1433

How to fix it

1Check the error detail for the failed activity 'WriteToDatabaseTableFrom_...' — confirm it is a TCP/port 1433 connectivity issue.
2Update firewall rules on the gateway server to allow outbound TCP port 1433 to these endpoints: *.datawarehouse.pbidedicated.windows.net, *.datawarehouse.fabric.microsoft.com, *.dfs.fabric.microsoft.com.
3To scope to a specific workspace, navigate to Fabric workspace → DataflowsStagingLakehouse → View Details and copy the SQL connection string.
4Workaround (if firewall cannot be changed): combine referencing queries into a single query.
5Work around the error by disabling staging on all referenced queries in the dataflow.

Frequently asked questions

Does this error affect all datasets using the same gateway?

Yes — all datasets routed through the affected gateway will fail simultaneously. Resolving the gateway configuration or credential issue restores all of them at once.

Does this error appear in Power BI Desktop?

No — Power BI Desktop connects directly to data sources. Gateway errors only occur when Power BI Service initiates a scheduled or manual refresh.

Can this error resolve itself without intervention?

No — gateway errors require manual action: re-entering credentials, restarting the gateway service, or correcting the network path between the gateway and the data source.

How long does it typically take to fix?

A simple credential refresh takes 5–10 minutes. Network or firewall issues can take 30–120 minutes depending on your infrastructure access.

Source · learn.microsoft.com/en-us/fabric/data-factory/gateway-considerations-output-destinations