Why does it say not enough free space in action replay?

The most likely reason that happened was while the action replay was saving you turned your game off don't do that i did it twice and well it sucks big time but in case you do it again save this to your desktop by copying and pasting on a notepad okay! the fix is simple: Try resetting the hardware by following these steps:

1/ With the console powered off, hold A+B.

2/ Power up the console while still holding A+B.

3/ As soon as the Nintendo screen is displayed, before our screen stating this product is not endorsed by Nintendo, press and hold Start and Select while keeping hold of A+B.

4/ Continue to hold these buttons until the Main Action Replay screen is displayed, then release. Your product is reset, and will accept codes once more.

EDITED BY YENIAUL:

You can also get the code manager, plug it in your PC, then press the "Delete all" button, then press "Commit Changes". Then, reflash your codes!