Issue getting shinies in dens

[Jittery]

So i have been trying to get mimikyu shiny to spawn in my den and I am doing the correct den and putting in seed AAD108AD464C87BB which is always a shiny and still it dont work. Do I have to beat the game to get that to work. Any info could help.

[Kaphotics]

Editing an old save causes the seeds to advance, btw.

Seed check whatever you catch to ensure it's from the right seed and not a later frame.

[theSLAYER]

I also advise toggling your Switch's date up or down one before you launch a save, to prevent any frame advancement from the date naturally advancing.

Artificial toggling of dates tends to stop that, allowing older saves to be loaded as is.