Hey @Grzegorz_Szurkalo can you tell me more about the error or share a screenshot?
The error that was run into above would have been triggered by an issue with the IAM Role having access to the AWS S3 bucket. This could be due to an improperly setup role, or it could be due to changes made to the role after configuring the federated database instance. For example, if you setup and were able to setup and query your S3 bucket, and then on the AWS console you edited something to dissallow use then it could cause this error.