This usually means the path to the .nds file is incorrect. Ensure the ROM is in the exact folder you specified during the CIA creation.
C --> E[Generate Unique Title ID]; D --> F[Convert Banner to 3DS Format]; convert nds to cia
This guide focuses on the "Forwarder" method, which wraps the NDS ROM into a container that the 3DS home menu can recognize and launch via the native Nintendo DS firmware (TWL_FIRM). This usually means the path to the