So I purchased the Canon speedlite transmitter and tried it with my Canon 600 ex-rt flash. I set transmiter/flash on same channel, synced and fired several times that I tried it, then it stopped firing? Could it be because the flash base is making contact with the stand I have it set on or the flash metal mount?
Try to simply put a piece of adhesive tape on the bottom of the accessory shoe in which the 600EX-RT is mounted, so that the central pin (trigger) in the hotfoot of the flash is insulated from contact with the surrounding metal of the shoe. Purely a shot in the dark fix, since I have no idea how you mount your flash remotely.
Also check the remote trigger settings to make sure you did not inadvertantly bump any settings so that the transmitter is not longer communicating to the flash, due to a change in channel or flash groups setting.

