Pokémon crystal can't hold a save despite putting in a new battery.

I recently bought a cartridge of Pokémon crystal from eBay. It was listed as working but having a dead battery. Once I got it I changed the battery but the game still can't seem to hold a save. I am getting mildly concerned that I may have damaged the cartridge during the battery swap. Otherwise I don't know what the issue could be. Any help is appreciated.