3DS + Pokemon Platinum troubles

[Gyousei]

this happens often with my old used copy of Heart Gold. use rubbbing alcohol to clean the contacts thoroughly, then make sure to blow off both the cartridge and the inside of the cartridge reader of the 3ds. If the game continues to not be read, repeat blowing out the 3ds cartridge reader until it works. that's all I can recommend. I hope this helps ^-^