That probably means you ran out of energy, or it overheated, or maybe it short-circuited. It's part of the game to figure out why it got stuck.
well i did play it multiple times and succeeded, I did like it because of it feeling like a REAL rover mission. I was able to avoid overheating by sand (hint: dont move on it until night, also if you just sit there during the day, it gets to "system temp critical," but nothing happens) short circuiting by water (dont do anything on it, try to move through it as fast as possible,) becoming the Spirit Rover (dont move on the gravel), losing electricity and it never waking up (use the solar cell and schedule it at the beginning of the day for maximum energy) and more hazards.