Does this happen with any DS(i) game? This probably means your TWL_FIRM got corrupted, a very common issue that happens when installing CFW. To fix, download TWLFix-CFW, launch it from the homebrew launcher, then perform a system update from system settings. This deletes the corrupted TWL_FIRM and redownloads a working version directly from Nintendo.
https://github.com/MechanicalDragon0687/TWLFix-CFW/releases/tag/1.3.1