Hey guys! I have a problem

I'm using my cousin's PC in when playing with emulators. My cousin and I have separate folders of everything so as not to accidentally overwrite our save files. Yesterday(March 25, 2017) I started playing Pokemon Platinum version. Everything was going fine for me but not for my cousin. I can save the game just fine but he can't. He tried using save states but still nothing, he still gets the same result. Every time he starts the game it always automatically begins with a "New Game". Then he made a new folder for his games, deleted his previous ROM file and copied a new one from mine. Then everything was OK for him. He can save normally including the save states.

Here is the problem. Now I'm the one who can't save anything. Every time I start the game it begins with a "New Game". I've checked my folders and everything is still the way it was, everything's still there. I've also checked my path settings and it was correct, my settings were unchanged.
We've played the same games and have never overwritten each other's files before, until this one.
My other games are working fine so I know my configs are OK(I think).

It seems like the PC or emulator only allows 1 Pokemon save file of the same version to be present, I don't know.
Is this a bug or something? Or maybe a broken ROM file?

PLEASE HELP!