two flashes using Plus X trigger, only one flash fires

[josephz1994]

I've got a Yongnuo YN-565EX attached to a Plus X on a stand using a pc sync cord
and I've got a Speedlight 600EX shoe mounted on my Canon t4i attached through a pc sync cord to a plus X

when i press the "test button" on the Plus X attached to the 600ex, both flash's fire

However when i take a photo from my t4i, only the flash 600ex attached on my camera fires and not the Yongnuo YN-565EX. Both the Plus X are on the same channel
this is really frustrating and i've got no idea whats happening, why isn't the two Plus X talking to each other when i take a picture !
Please help

 

[Lawliet]

However when i take a photo from my t4i, only the flash 600ex attached on my camera fires and not the Yongnuo YN-565EX.

Because the sync port on the 600EX is input only, it can't send a signal.

 

[josephz1994]

However when i take a photo from my t4i, only the flash 600ex attached on my camera fires and not the Yongnuo YN-565EX.

Because the sync port on the 600EX is input only, it can't send a signal.

best solution ?

 

[Ian_of_glos]

Connect the pc sync cable to the camera not the flash. There is a bit of a lag but it should trigger the remote flash shortly after the on camera flash fires.

 

[FEBS]

Another possibility is placing the Yongnuo YN-565EX in the S1 mode, in which he will be triggered by the light output of the 600EX