The only other thing to check is that all your config options are properly named. See https://docs.blesta.com/display/user/Soft+Auto+Installer#SoftAutoInstaller-Usage
script
admin_name
admin_pass
directory
For example: https://docs.blesta.com/display/user/Soft+Auto+Installer?preview=/13664345/13664356/config-option-script.png#SoftAutoInstaller-Usage
.. Edit: And of course that the plugin is installed. If it still doesn't work, uninstall and re-install the plugin.