Amazon S3 AFU fails to upload

Hi,
i have a pearl mini with afu enabled, im trying to upload to an amazon S3 server, i manage to do that in the past but now when i try with another pearl and another bucket i cant remember how i got the session token.

i tried with postman to sts.amazonaws.com and i do get a session token in return, but when i enter that in the pearl mini its fails:

Dec 10 07:25:29 PLMGSAA753794 user.warn afu[14399]: S3 Upload failed: An exception occurred while initiating a multipart upload: Error executing “CreateMultipartUpload” on “https://pearlmini.s3.eu-west-2.amazonaws.com/HDMI-A_Dec10_07-14-07.mp4?uploads”; AWS HTTP error: Clien

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