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Hello @Martin Hansen , I hope you are doing well,
You are correct that Azure Owner and Synapse Administrator are different roles. However, Microsoft provides a recovery mechanism for exactly this situation when the original Synapse Administrator is no longer available.
Since you have Owner access through the subscription, you should be able to manage Azure RBAC assignments on the Synapse workspace. If Synapse Studio returns "Failed to add the role assignment", I recommend trying the assignment through PowerShell instead of Synapse Studio.
For example:
New-AzSynapseRoleAssignment `
-WorkspaceName "<workspace-name>" `
-RoleDefinitionName "Synapse Administrator" `
-ObjectId "<your-Entra-object-id>"
Microsoft also documents using the role definition ID directly when the user has Azure RBAC permissions but is not yet a Synapse Administrator:
New-AzSynapseRoleAssignment `
-WorkspaceName "<workspace-name>" `
-RoleDefinitionId "00001111-aaaa-2222-bbbb-3333cccc4444" `
-ObjectId "<your-Entra-object-id>"
The second approach can be useful because resolving the role by name may itself require permissions that you don't yet have.Before running it, verify that your Owner assignment is effective at the Synapse workspace scope or above, and that you are working in the correct Microsoft Entra tenant.
Once the Synapse Administrator assignment is restored, you can manage the remaining Synapse RBAC assignments from Synapse Studio > Manage > Security > Access control.
References:
Manage Synapse RBAC role assignments
If the PowerShell assignment also fails despite the effective Owner permission, please provide the exact error returned by New-AzSynapseRoleAssignment (with tenant/subscription IDs redacted). That will help determine whether this is an Azure RBAC permission issue or a Synapse backend issue.
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