Unlike a Prius, stepping on the brake does not increase the amount of regen. Only less pressure on the accelerator causes regen. If you have a new X Raven (post March-2019) regen should bring you to a stop. Earlier X will get to very slow, but not a stop.
If your battery is cold and the display shows dotted yellow lines on the energy circle, regen is very limited to none. As the battery warms, the yellow dashes disappear and regen will be effective again.