Those who follow Ackman have done buying this stock after Ackman had purchased at $100, chart shows. Those who already hold this stock before Ackman are not selling although they see paper gains hoping Ackman knows something. Bargain hunters see no value in this stock, those had held this stock see no reason to sell(at least for now). That is why this stock is standing still with no trading volume.
Problem is this stock will be stuck at this price while all other stocks rally. People begin to get agitated over others having party while this stock is stuck, concern about opportunity cost. Then, few will start selling this stock which will trigger more, then people begin to get nervous when this thing gets below $100. One thing leads to another 100 becomes 95 to 90...... When it gets below 85 (pull 10 year chart, it is overbought now) Ackman will be squarely blaming on APD management for incompetence, instead of understanding his buying at the top. Tension between MGMT and Ackman thickens. Next thing you know Ackman is out hunting for a new CEO. CEO is losing his focus and next thing you know APD will be following exact chart pattern of JCP. Sad story but that's what happens when you entrust too much money in the hands of kid who always had easy life, so far at least.
It seems to me that the real issue is What does Ackman want the company to do? Assuming they don't agree to greenmail, how does he get out? I don't think anybody buys this company. I don't see a fit. So all he can do is make suggestions as to how they can run it better; make more money; increase the dividend; push up the stock price; and then try to sell in the open market. This is a slow process extending over several years and management could easily ignore him. Meanwhile, he has money tied up.