If you are reading this, you are likely part of a very specific Venn diagram: You love portable football (soccer), you own a V1 unpatched Switch or a modded OLED/Lite, and you are eagerly awaiting (or searching for) the latest EA Sports title.
Ensure your .nsp file is complete and not corrupted. If the file is split into smaller parts (often named .nsp.0 , .nsp.1 , etc.), ensure all parts are in the same folder on your microSD card.
Have you found a working FC 26 NSP? Let the community know in the comments (but don't post direct links, obviously).