WinSCP with S3

Hello, I would like to know how I can get the list of buckets because I can connect with C#, but it doesn't let me upload, telling me "the bucket does not exist." However, with the same data from the program, I can do it perfectly. If you need more information, please let me know, and thank you in advance.

As in the GUI, even in the .NET assembly, the buckets are presented as root-level folders.
See https://winscp.net/eng/docs/guide_amazon_s3#buckets
So listing the root folder will give you bucket names. E.g. in C#:
That also means that to upload to the bucket, you need to use the bucket name in the target path: