Why can't I migrate Pokemon from gen 3 Sapphire to gen 4 Platinum?

I was looking at all of the other similar questions, but none of the other users had exactly the same issue as I am, so any help would be appreciated.

I recently bought a copy of Pokemon sapphire from a local store, and I’m positive that it’s not a bootleg (I did a lot of research to be sure of this). I was planning on transferring some of the starter pokémon to my Pokemon platinum before I started playing sapphire for real, but whenever I go to the menu on Platinum, no “migrate Pokemon” button comes up.

On platinum, I’ve beaten the elite 4 and obtained the national dex. I’ve been to the pal park and had a tour by the warden. Everything on that end seems like it’s correct. On sapphire, I have eight Pokemon, six in my PC (none of which know HM’s) and two in my party. I’m only in the first town with a Pokemon center, but from what I understand that shouldn’t be a problem.

I’m also sure that my copy of Platinum is legitimate. I’m playing the two games both on the DS Lite, and when I attempt to migrate both games are inserted and clean. Does anyone have any ideas as to what might be the issue?

(Additionally, I’ve also tried to migrate onto my Soul Silver and White games, but neither of those work. I have the national dex on Soul Silver, but not on White. I purchased Soul Silver from a reputable seller here and I bought White brand-new when the game was issued.)

Thanks guys!

Pleaselog inorregisterto add a comment.

This question has been answered through the comments to the question, so I’m just putting this here so any future people with the same problem can see. The copy of Sapphire turned out to be fake, which caused the issues with migrating. The cartridge looked almost identical to that of an original copy, but the circuitry inside looked nothing like it was supposed to. I have since purchased an actual copy, and the problem has been fixed; I’ve had no problem migrating since. Be careful when buying GBA games, guys!