Please verify the following points:

• Transmitter and receiver must have the same frequency channel settings.
• Transmitter and receiver must have the same synchronization mode settings: Normal or Speed sync mode (ELSP MODE on the Transmitter Pro).
• Check that the EL-Skyport receiver in all EL units with built-in receivers is switched ON.
• Try another frequency channel for both transmitter and the receiver of the Elinchrom unit.
• Reduce the distance between the flash unit and transmitter.
• Check the hotshoe fitting.
• Check the camera settings (turn hotshoe communication on).
• Check that the Transmitter Pro version corresponds to your Canon, Nikon, Sony, or Fujifilm camera.
• Check the list of compatible cameras.

Learn more about Speed and Normal sync mode.