How can I determine why my output.manifest isn't being created?

I'm getting the following messages.

• FAILED: ClientError: Initial probe with 10 objects failed. Look at the output manifest file for details.
• 401 UnknownError: The specified key <path>/manifests/output/output.manifest isn't present in the S3 bucket <bucket>"

I'm new to this so I don't know the best places to look to debug, but I have tried to find and read the logs. I've tested the lambdas individually with mock data (pre-processing lambda) and an s3 annotation file (post-processing lambda), but not tested the full pipeline. One weird thing is in one of my attempts, somewhere, I found a consolidated file that included a structure like: {'content': {'example-attribute': and I have no idea where "example-attribute" can be coming from.

Appreciate any help you can provide.