Why won't my pokemon ruby save?

Answer 1

One possible problem could be wear and tear on the internals of the game cartridge. This is more likely if the game was bought used or if the game used to save properly but now does not. If the game never saved properly and was not bought from a reputable seller, it is possible that it is a fake copy of the game. A few telltale signs are the cartridge itself not being red and slightly transparent or the label being crooked or not shiny. Despite common beliefs, this is not an issue with the battery. With Pokemon Ruby, the internal battery of the cartridge only controls the internal clock. While clock-based events, such as berries growing, will not function if the battery is not working, saving is completely unaffected.

Answer 2

it could be fake,

you can tell if its fake by simply looking at the game cartridge,

if your ruby is not a ruby coloured cartridge then there is a high chance that it is fake and that it might not save