Well I used the 3ds another user referred me to... But it turned out to be the exact one I had. My NN3DSXL *US* will not load into DevMenu. This was an issue with me before. I simply used BBM before, but now that is not possible.
To clear things up, if I run GW Mode in sysNAND or emuNAND, I cannot load DevMenu. After selecting it in the Multi-ROM, I go to load, and it just black screens. I can either Power off the system, or I can take out my GW card, where the system complains about the cart being removed, and then power off anyway.
I can load BBM on both sysNAND and emuNAND but clearly it won't install the mset. Any advice?
Gonna try a different SD card. Though I have a legit card, I think perhaps something to do with it being exFAT or 64gb, or fragmentation... IDK....
^ That worked... Finally got DevMenu to load up in my NN3DSXL. Now to install mset. Yep no problems with the importa. It (the CSU) just wasnt playing nice with my mSD card (the one that goes in the redcard)