Hi. I think you are missing allowing service principal in PBI admin portal, not just to the admin API but for the whole service. You can also try adding permissions to the App registered for PBI Service or grant Admin concent to all permission (only an admin can do that). You can follow this post (that is preparing ADF to refresh and not using the admin) to check if you are missing something. https://blog.ladataweb.com.ar/post/642023841877671936/azuredatafactory-actualizar-powerbi-con
You can also try the requests writing code to know if the Service Principal is working and it's an ADF issue or if it's not and the problem is the configuration.
I hope that helps,
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