Automate Dataflow export to .json through Power Automate or Azure Logic Apps

You need to replace in the URL https://api.powerbi.com/v1.0/myorg/groups/{groupId}/dataflows/{dataflowId}

{groupId}: This is the workspaceId where you have the dataflow

{dataflowId} This is the dataflowId

If you open the dataflow in PowerBI Service the URL reads something like this:

https://app.powerbi.com/groups/xx9xx9x9-x9x9-x9x9-x9x9-xx9xx9x9x9x9/dataflows/xx9xx9x9-x9x9-x9x9-x9x9-xx9xx9x9x9x9?experience=power-bi

GroupId in the Basic URL is the ID between groups/ and /dataflows/

DataflowId in the Basic URL is the ID between /dataflows/ and ?experience

You will need to authenticate using your user/pasword (same credentials as you use to log in to Power BI).

The only other thing to check that I can think of is that you have the Tenant Setting to run REST API calls enabled which I believe is in Integration Settings (but not 100% sure) Integration admin settings - Microsoft Fabric | Microsoft Learn

Hope this helps.