DMX Splitter help


This is hard to explain but I will give it a shot!

I am having issues with a DMX Splitter,

Basically we have 2 different sets of Dimmers. One controls the FOH Bars and one controls the On Stage bars. 

I have control of the FOH Bars from the desk no problem but I can't seem to gain control of the Stage rig.

I have tried everything!

I have re-patched all dimmers 1:1 and all settings are exactly the same on the FOH dimmer as the stage one however I can't control the stage lights. I can turn them on manually (Setting the channel levels from the dimmer itself) but I can't use the desk. 

I have an image of the splitter we have to control the on stage lights below if anyone can help please