If you are trying to connect to the server via SFTP and are getting the error below (even though your username and password are correct) it is likely caused by a deprecated server protocol. You can fix the issue by re-enabling legacy RSA/SHA1 in your Dreamweaver config file as a workaround to establish the connection. To do that, follow Adobe's troubleshoot instructions.
Note: This issue has been happening with newer Dreamweaver versions due to a change made by Adobe.
