The antonyms for the phrase "made headway" would be "stagnant," "fallen behind," or "regressed." When someone says they have "made headway," it suggests that they have made progress towards a goal or objective. However, if they have not made headway, it means they are not moving forward in any way. If they are stagnant, it means they are not making progress at all. If they have fallen behind, it means they were making progress before but have not kept up with the pace. And if they have regressed, it means they have moved backward from where they were before.