I bought a leappad2 for my 3 yo as a Xmas present. I bought three cartridges today from toys runs but none of them work. I put the cartridge in and the on screen cartridge icon comes up with a red cross and unplayable. I thought it might be. Cartridge problem (wrong type or faulty) but they all say explorer on them and I can't believe that all 3 are faulty.

Am I doing anything wrong here or does it sound like a faulty unit? I have a recipet (sainsburys) but have chucked the packaging.