On some flashcarts this doesn't work and anyways why do you even want to soft reset? Why is it so intriguing?
i need to soft reset so i can get a shiny starter cause i don't wanna turn my Dsi On and off and on and off again and again
Well, you can always try to do the reset on the r4 scree,n. If it goes white, don't turn off, just press the "games button" (At least where it was located) and run the game again. Works for me (R4i SDHC)