the CIA file you are trying to install is corrupted, incomplete, or incorrectly signed for your system Primary Fixes Re-download the CIA File
If you still get the error after importing the seed, reply with:
Result code: 0xd8e0806a Level: Permanent (27) Summary: Invalid argument (7) Module: AM (32) Desc: (6a)
Sometimes the 3DS "remembers" a failed installation, preventing a new one.
In plain English:
The infamous "Failed to install CIA file" error!
If you are transferring the file via a microSD adapter, ensure the adapter isn't faulty.