For anyone working in Workday and having S3 Connection issues, FYI this might be helpful.
After much trial and error (emphasis on the error piece), we learned that Workday's "Test Transport" functionality doesn't work for S3.
The following configuration is what did the trick for us:
Delivery Method:
Amazon Simple Storage
Bucket Name:
us2-prod-demotenantbucket
Region:
US West (Oregon)
File Name (path and file name):
system-defined/********-****-****-***********/MDA-Data-Ingest/input/*file_yyyy-mm-dd.csv]
Thanks.