There are a few reasons your memory foam topper may have gotten complicated. The first reason is that the Topper may be too old. Memory foam generally has a lifespan of about three to five years. After that, the foam begins to break down and can become hard. If your Topper is over five years old, it's probably time to replace it.
The second reason your memory foam topper may have gotten hard is that it was not adequately cared for. Memory foam must be kept clean and dry to maintain its softness. If the Topper gets wet or dirty, it can become hard. Be sure to follow the care instructions with your memory foam topper to keep it in good condition.
The third reason your memory foam topper may have gotten hard is its exposure to extreme temperatures. Memory foam can become complex if it gets too cold or too hot. If you live in a climate that experiences extreme temperatures, you may want to consider storing your memory foam topper in a temperature-controlled environment when you're not using it.