Verify that identity-based authentication or networking restrictions are fully configured. Azure RBAC grants share-level permissions, but the storage account must also be configured to authenticate your identity and allow access to the storage data plane.
The first thing to check is the identity source configuration. In the Storage Account, go to File shares and check Identity-based access. If it is not configured, you need to configure an appropriate directory service, such as Microsoft Entra ID, Microsoft Entra Domain Services, or on-premises Active Directory Domain Services, depending on your environment. As an alternative for testing, you can configure the default share-level permissions to provide authenticated users with the appropriate Contributor access.
If you are accessing the file share through SMB, also check whether TCP port 445 is blocked. Some ISPs, firewalls, or network devices block outbound SMB traffic. If port 445 is unavailable, you will not be able to mount the Azure file share using standard SMB from that network. In that situation, you can use a VPN or Azure ExpressRoute to provide connectivity, or use Azure Storage Explorer, which can access the storage account without requiring a direct SMB connection.
You should also check the Storage Account networking configuration. Go to Storage Account > Networking and verify whether access is restricted to selected virtual networks and IP addresses. If so, make sure the public IP address of the client you are using is permitted, or temporarily allow access from all networks for testing. If the upload works after changing the networking setting, the firewall or network configuration is the cause.
Finally, if you assigned the RBAC roles recently, allow some time for the permissions to propagate. You can also completely sign out of the Azure portal and sign back in to obtain a refreshed authentication token. If the roles have been assigned correctly and the issue persists after propagation, focus on the identity-based access configuration and the Storage Account networking settings, as those are separate from the RBAC role assignment.
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hth
Marcin