Power BI Error:
AADSTS50102

What does this error mean?

Microsoft Entra ID (Azure AD) cannot load the CustomClaimsTransformer assembly configured for the application's claims-mapping policy.

Common causes

• 1A claims-mapping policy assigned to the service principal references a CustomClaimsTransformer type that no longer exists or was renamed
• 2The claims-mapping policy JSON contains a typo in the transformer's fully-qualified type name (namespace.class, assembly version)
• 3The custom transformer assembly was never (re)deployed to the tenant after a rebuild or migration
• 4AcceptMappedClaims / custom signing key requirements aren't met, so Entra ID refuses to load the transformer
• 5The policy is still attached to the service principal but the transformer was deprecated as part of an Entra ID schema cleanup

How to fix it

1. 1Run `Get-AzureADServicePrincipalPolicy -Id <servicePrincipalId>` (or Graph `servicePrincipals/{id}/claimsMappingPolicies`) to find which claims-mapping policy is attached and producing the error
2. 2Inspect the policy's `ClaimsTransformation` definition and verify the `TransformationId` / type name matches an actually deployed CustomClaimsTransformer in the tenant
3. 3If the transformer is obsolete, detach the policy with `Remove-AzureADServicePrincipalPolicy` or update the JSON to remove the broken `ClaimsTransformation` entry
4. 4If the transformer should exist, redeploy the assembly and re-create the policy with `New-AzureADPolicy -Definition ... -Type ClaimsMappingPolicy`, then reassign it to the service principal
5. 5Confirm the app manifest has `acceptMappedClaims: true` (or a custom signing key configured) — without this, Entra ID blocks the transformer from loading
6. 6Test sign-in again and capture the correlation ID; if it still fails, open a Microsoft support case with that correlation ID — broken transformer assemblies often need backend assistance

Frequently asked questions

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