Hi Reza,
Hope you are doing good.
Can you first make sure that the user that you are using has access to the administrator role or has the administrators group assigned to it?
If the issue persists, Kindly run the web diag tool as outlined in note 1045019- "Web diagtool for collecting traces" with "Security" -> "All" and reproduce the issue.
Clear all the cache before starting this. Start the web diagtool from the time you login to the engine and make sure that the number of clicks are kept to the minimum and let us know the time and the 'user' employed. Run this on server node 0 (check note 1589567).
Attach the output to the forum.
Thank you!
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Kind Regards,
Hemanth
SAP AGS