The SIM Toolkit (or STK) isn't like a normal app you download; it’s an interface for small applications physically stored on your SIM card. When it breaks, it’s usually because the communication between the Android OS and that tiny chip has been interrupted by:
The system app managing the toolkit might be stuck in a loop. The "Bring It Back" Playbook Android Sim Toolkit Not Working
A recent OS update (like the jump to Android 14 or specific manufacturer skins) might have broken the link. The SIM Toolkit (or STK) isn't like a