The flash should be set in Manual mode, not Slave mode. When used in Slave mode there must be a Master flash optically controlling the 430EX II through the optical receiver on the flash. In Slave mode the signals through the pins on the flash shoe are ignored. If there are channel and slave symbols visible in the lower right corner of the 430EX II's LED panel, press and hold the Zoom button (for around 1-2 seconds) until they disappear. This will probably put the flash back into E-TTL mode so you will then need to press the mode button until M appears on the LED screen.
If the flash is set in Manual mode then you need to check your Cybersync trigger set to be sure they are set to the same channel and communicating properly. Exactly how you need to do that will vary depending on exactly which Cybersync models you are using. There are too many possible combinations to cover them all here. Please see the CyberSync User Manual on how to setup your particular models.
Beyond that, you can also test the flash directly on the camera's hot shoe just to confirm that the hot shoe and flash are working properly. Also check to be sure all the pieces are connected properly. With some triggers it is very easy to insert them backwards on the camera's hot shoe or insert the flash backwards on the flash adapter. And don't forget to check the batteries powering your various pieces as well!