The issue is solved by the development version you sent me.
I can connect through the BackBlaze S3 API.
BackBlaze is only supporting AWS V4 signature process, not V2.
Is WinSCP capable of supporting V4 signing ? Is there any way in WinSCP to select V2 or V4 signing process; I couldn't find anything related in the Advanced site settings.
I'm using latest version of WinSCP on Windows 10.
Somehow I managed to post as a guest...
BackBlaze announced a week ago they supports S3 API.
However, I'm unable to connect with WinSCP to BackBlaze. WinSCP comes back with following error message: "Connection failed. Invalid request parameter received: max-keys".
I made sure the API key has permission to list all buckets.
Could be user error of course, but I have no problems connecting to e.g. Wasabi with WinSCP.
Attached is the log file, hope you can see where the problems lies.
I took out the keys: I could supply them when required.