I am running R7 with EF 10-18mm, Godox V850II which has all been working fine. Purchased an x pro transmitter today and I can get the x pro to trigger the flash by the transmitter lightning button but when I attempt to press the shutter to snap a photo the flash does not trigger.

The flash is connected to the same group and channel and it is set to slave. The camera is set to EFCS.

Am I missing something simple?