Hi, I think it's because you have Unit=Bytes. The defined unit for BytesDownloaded is None. Try omitting "Unit" from your query.
From the boto3 documentation:
In a Get operation, if you omit Unit then all data that was collected with any unit is returned, along with the corresponding units that were specified when the data was reported to CloudWatch. If you specify a unit, the operation returns only data that was collected with that unit specified. If you specify a unit that does not match the data collected, the results of the operation are null. CloudWatch does not perform unit conversions.
Also make sure you're querying us-east-1 (you're probably already doing that).
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