s3 upload and role to assume?

####Task Permissions
This task requires permissions to call the following AWS service APIs (depending on selected task options, not all APIs may be used):
* s3:CreateBucket
* s3:HeadBucket

Content uploads are performed using S3's PutObject API and/or the multi-part upload APIs. The specific APIs used depend on the size of the individual files being uploaded.
2021-03-05T21:05:31.7167617Z ==============================================================================
2021-03-05T21:05:32.2450994Z Configuring credentials for task
2021-03-05T21:05:32.2451608Z ...configuring AWS credentials from service endpoint 'xxxxxxxxxxxxxxxxxxxxxx'
2021-03-05T21:05:32.2451962Z ...endpoint defines role-based credentials for role ***.
2021-03-05T21:05:32.2452332Z Configuring region for task
2021-03-05T21:05:32.2452695Z ...configured to use region us-east-1, defined in task.
2021-03-05T21:05:32.2452892Z Configuring region for task
2021-03-05T21:05:32.2453262Z ...configured to use region us-east-1, defined in task.
2021-03-05T21:06:56.7196637Z ##[error]Error: Bucket xxx123 does not exist or you do not have access. Auto-create option not set, cannot continue.

So in service connection I've defined:
Access Key
Secret Key
Role to assume
Role Session Name

But I feel like I'm not really assuming the role and therefore not being granted access.
Is there a simpler way to test if assume role in extensions is actually working?
Am I missing something here?

Thanks for any help provided

Start by reproducing the Azure DevOps AWS upload task with the service connection settings and compare its credential and region logs with the bucket-access error. Done means determining whether the configured role is assumed and whether the resulting credentials can access the named bucket and upload content.

Written by the indexing model from the issue text.