Composite model connection could not be made.

Following links will also help you about this issue:

Composite Models on Power BI Datasets and Analysis Services Models – SumProduct

Solved: Composite Model: Build permission needed for end ... - Microsoft Fabric Community

Use composite models in Power BI Desktop - Power BI | Microsoft Learn

Setting the right permissions for users of composite models - SQLBI

Build Permission for Shared Semantic Models - Power BI | Microsoft Learn

Update to required permissions when using composite models on a Power BI dataset | Microsoft Power BI Blog | Microsoft Power BI

powerbi-docs/powerbi-docs/connect-data/service-datasets-build-permissions.md at main · MicrosoftDocs/powerbi-docs · GitHub

notsobad__ 

Yes — users must have Build permission on every underlying semantic model. App audience access gives Read only, which is not enough for composite / multi-dataset reports.

Why the error appears:
Power BI connects via Analysis Services (XMLA). Without Build, the connection fails and shows this generic error.

Fix:
Grant affected users (or a security group):

• Build permission on each dataset
  Semantic model → Manage permissions → Enable Build

Notes:

• Workspace Viewer + App access ≠ sufficient

• This is by design, not a Microsoft bug

• Error message is misleading but common

Best practice:
Use a thin central semantic model and grant Build only on that model.