BigFix takes the exit code from the installer.
Are you sure the installer is silent? Or can the user cancel it (no idea how when it’s silent)?
To see the parameters for an exe, you can use
Avaya one-X Communicator Suite.exe /?
Then you will see the possible parameters. The l*v is normally for msi’s.
So as @TheTick mentioned, try the installation first manually to see if it’s really silent.
edit: please avoid to post your servername etc on the fora. Blur it out or replace it with “x” or something (in your first post)