New dataflow to "Azure Synapse Analytics Workspace" with service principal

Good day

I'm trying to create a new dataflow from within Power BI Service to an Azure Synapse Analytics workspace using the Azure Synapse Analytics workspace (Beta) connector. 

I am getting a non-descriptive error when trying to connect using a service principal, so I'm unsure of where I am going wrong. 
(screenshot below). When I connect with an organizational (Azure AD) account I am able to connect successfully. 

My organizational account and service principal both have the same rights:

• Resource group - Owner / Contributor
• Storage account - Owner/ Contributor/ Storage blob data contributor 
• Azure synapse anaytics workspace - Owner / Contributor / Synapse Administrator 

When I connect using the same connector directly from Power BI Desktop, there is no option to connect with a service principal - you can only connect with an organizational account. 

Does the connector perhaps not fully support authentication with service principals yet (as I notice it's in Beta)? This would explain why service principal auth is not available from within Power BI Desktop. 

Any help or advice would be appreciated. 

Power BI setup steps 

Select Workspace
   -->+ New
   --> Dataflow
   --> Add new tables
   --> Azure Synapse Analytics workspace (Beta)