I just updated Winscp from 5.11 to 5.17. My bath script only use username@server and private ssh certificate. My script used to run OK in 5.11, but after Winscp was updated to version 5.17, the batch ask for password after trying to authenticate with username@server + private ssh certificate. If I launch WinScp GUI, all looks OK. So as a workaround i had to roll-back to 5.11.