If your server is configured with deprecated OpenSSH protocols, re-enable legacy RSA/SHA1 in the Dreamweaver config file as a workaround to establish the connection

In Windows:

1. Close the Dreamweaver application.
2. Type RegEdit in the Windows search bar to run Registry Editor app.
3. In the left pane of the Registry Editor, navigate to the following path:
4. HKEY_CURRENT_USER\SOFTWARE\Adobe\Dreamweaver 2021\Site Preferences
5. Find Use SFTP Legacy Algorithms From Config File and set it to TRUE.
6. Close RegEdit.

See https://helpx.adobe.com/dreamweaver/kb/troubleshoot-sftp-server-connection-issues.html