Whenever I link up my two DSes, it says that there are not enough Pokemon in my PC, even though there are. Has anyone else experienced this? What do I need to do?
Make sure your PC Pokémon are valid
The Poké Transfer requires a full set of six Pokémon in your Generation IV game PC to transfer to your Generation V game. While you don't have to actually transfer all six Pokémon (by failing to capture some of them in the following minigame), you still require a full set of six to begin the transfer process.
Further, some Pokémon can't be transferred. These include Eggs, Spiky-Eared Pichu, and Pokémon with HM moves. If you don't have at least six Pokémon that are valid to transfer, you won't be able to start the process. You may need to catch some filler Pokémon, delete some HM moves, hatch some eggs, or just give up on transferring Spiky-Eared Pichu, depending on the Pokémon you're trying to transfer.