2 Gateways, one Fabric warehouse

Thankyou, lbendlin, for your response.

Hi BartoszBudnik,

We appreciate your inquiry through the Microsoft Fabric Community Forum.

Based on my understanding of the issue, utilizing separate Dataflow Gen2 instances for Server A and Server B via different gateways is the supported approach to load data into a single Fabric Data Warehouse. Since you are encountering errors while connecting to Server B via its gateway, kindly follow the steps below, which may help resolve the issue:

1. Verify that the gateway for Server B is online in Power BI Service. Ensure that port 1433 is open on the network for outbound SQL traffic.
2. Check that the credentials mapping in Dataflow Gen2 matches what is set in the gateway.
3. Confirm that you have permission to use the gateway and its associated data source.
4. Attempt to recreate the data source under Manage Gateways with the correct settings.

Once the issue is resolved, both dataflows can load into the same Data Warehouse. Subsequently, in Power BI, you can connect to the Data Warehouse, create relationships, and schedule report refreshes.

Additionally, please refer to the following link for further information:
On-premises data gateway considerations for data destinations in Dataflow Gen2 - Microsoft Fabric | Microsoft Learn

If you find our response helpful, kindly mark it as the accepted solution and provide kudos. This will assist other community members facing similar queries.

Thank you.