"The game can be played" means that you have a fake cartridge. Real cartridges would say "The internal battery has run dry. Time-based events will no longer occur, but the game can be played" or something similar; fake carts don't have batteries, so the message was hacked as not to arouse suspicion.
If the game was bought on eBay or Amazon, and the box came flat-packed, it's a fake. Real games never come in flat-packed boxes.