Maybe the magnet isn't powerful enough or it's in the wrong spot.I have successfully injected ntrboothax into my system, and now I have to hold (Power) + (Start) + (Select) + (X) for several seconds to boot into SafeB9Installer to install boot9strap. I put the magnet in the place that puts my 3DS into sleep mode and have pressed the button combination many times, but nothing happened, so I'm at a loss in how to finish installing Luma on my 3DS.
When you try booting the console with the buttons held does it actually boot the system in sleep mode? (home menu appears immediately when you remove the magnet after waiting like half a minute to make sure the system has had time to boot)
If so I believe that means that ntrboot loaded successfully but it couldn't find boot.firm on the SD, since normally the system won't boot while in sleep mode, so it would take some time for the home menu to appear once the magnet is removed. The default behavior of ntrboot is to boot the system normally if boot.firm isn't found.
You can actually do the whole process without any help from other people now, though you still need to find a CtCert somewhere and you still need a PC for the bruteforcing. If he can't figure out ntrboot though then seedminer will be even harder.There's also the $2 seedminer method, which someone can brute force a file for you then you can install boot9strap from there.
Or somoene can troubleshoot your ntrboot issue and work with you on it. Meet me on Discord if you want some personal assistence.