Getting a video splitter to work with HDMI to SDI converter

Okay, so here's what my setup looks like:

My church has a computer running projection software, and we're wanting to use it to control two different screens. We purchased a Matrox DualHead2Go Digial ME that connects to the Mini DisplayPort on the back of our Mac Mini that control the software. That then basically expands that single Mini DisplayPort into two displays, one for each projector, that creates one big image stretching across both screens. From the Matrox unit, we're running a super long HDMI cable to one projector, which works fine, but then we're running the other HDMI into a Blackmagic HDMI to SDI micro converter, which then runs about 50 feet away via SDI to another Blackmagic SDI to HDMI micro converter, then into the second projector via the HDMI out on the converter. For some reason that signal isn't making it to that projector. I've checked and it shows on the "Display" window that I have a large display stretching across the two displays, so I know that part is working, but how to do I get it to where the HDMI to SDI converter is able to take the image being put out from the Matrox unit to the SDI to HDMI and then into the projector? Do I need some kind of HDMI to SDI hardware that has scaling or something? Is there a software solution that anyone knows of? I realize I could just run HDMI out to the second projector, however the distance is so far that I really don't want to risk performance/image issues by running HDMI that far. Any help would be greatly appreciated! Thanks!

Here is a suggestion
Test the cables first
Try sending a signal from the projector back to the source If it works
That will determine if the projector is not getting a signal or you have a bad cable from the source
Split the problem in half and then take the next step to figure out the problem

The converter you have accepts only strict smpte standards, the matrox dual and triple head boxes are notorious for being sketchy and not giving proper control over resolution, ie not being able to output a smpte compliant output from each output. Try different resolutions on the matrox, try switchresx on the matrox output, but realistically you are better to use something that accepts non smpte standards and can then scale and convert to SDI like the datavideo da70, there are a lot of other options. Or if you had used a datapath unit instead of the matrox it would have been fine. This has come up a lot on the forum, I think I have answered this at least a few times.