I downloaded the 5.14.1 8909 build developer version in case the region detection issue in teh tracker was my problem, but I don't think it is.
I have a set of S3 credentials for an S3 bucket in us-gov-west1 that I can test with filezilla pro and cloudberry, so I know the credentials and path are good.
IN Winscp, I get
Extra Details: RequestId: 5D738AFD9ADB305B, HostId: Xd4q7BJ5QoMNXEqBje7FDQU/bvHEYx21fe4TIyXXpaIBJNT1zsB3xJ28lJ5TMILmv1Wed7HylUY=
With the credentials that work elsewhere. I have another credential that works in both places. These both go to the same bucket, same URL, very confused.