WinSCP FTP won't connect to Windows Server 2019 IIS 10

Using WinSCP release 6.1.2 build 13797, Commander i/f. WinSCP has worked on this server for several years. Just upgraded to Windows Server 2019 with IIS 10.x hosting FTP. Fails to connect on various combinations of settings.

Case 1. Server set to connect using FTP and Port 21 - Response: Connection failed. Policy requires SSL. This is true. FTP with SSL on port 21 is required for connections to server.

Case 2. WinSCP set to FTP, TLS/SSL Explicit Encryption TLS 1.2 port 21 (min + max), Reuse ... Unchecked. No need for Cert file. Response: TLS connection established. Waiting for welcome message... Access denied. Edit box for password at bottom of failure screen. Password already saved. Still does not work if password added.

Server Admin has not used IIS to host FTP previously. Can you suggest any WinSCP or IIS FTP Settings to change?

Can you login with any other FTP client? Why do you think this is WinSCP issue? Did you check server log file/event log?

We think that the IIS v10.x settings is the issue. Log shows that the connection succeeds then replies Waiting for Welcome Message. Then can't connect. Any ideas as to correct FTP or SFTP settings for IIS 10?

Sorry, I do not know much about IIS.

(Btw, IIS does not support SFTP).