Use the SFTP Check if Connected action to validate if the connection to the SFTP server is still valid.
Optionally reconnect to the SFTP server (using the details from the SFTP Connect action) if the connection has been lost.
If the connection is detected to be disconnected then checking this box will attempt to reconnect the user. If the single attempt fails to connect to the SFTP server then the action will fail with the reason for the failed connection attempt.