Since you know it's ARM11 it means you have Luma3DS. As such, please post the COMPLETE info. Dunno, take a picture of 3DS with the error screen with your phone or anything.
Two most likely cases:
1. Game uses new cryto and you don't have the seed. Either launch eShop which will auto download it, or open FBI and go to titles, find the title in question, select it and pick the download seed option.
2. You are getting the 0xc960454b error, which means the SD card is corrupted. You can attempt to fix it by copying everything to PC, reformatting the card and copying all files back, if it doesn't work you will have to buy a new card.