Hi @gdschld ,

what ID have you used here:

"sts:ExternalId": "<STORAGE-CREDENTIAL-EXTERNAL-ID>"

I haven't done this for some time and got a bit confused with this STORAGE-CREDENTIAL-EXTERNAL_ID. I used to put there Databricks Account ID.
I found this, it might help: 
https://kb.databricks.com/unity-catalog/aws-s3-storage-credential-validation-failure-due-to-external...