The laser wears out over time, it's just inevitable, and on a PS2 from 2005 honestly it's a miracle it lasted this long! One dumb thing to try before you put it away: make sure the console is completely level, not tilted at all, because sometimes even a slight angle can disconnect the laser. If that doesn't help, you can also try dimming the blinds or lights in the room a bit while testing - sometimes a photo sensor that's a bit sensitive reacts badly to ambient light. After that, it's true that a tired laser is the most likely explanation, and unfortunately you can't really fix it without replacing the whole unit!