There is a glitch in the system on this level. I have almost completed this level multiple times, but as soon as my diamond drops through, the line disappears and my other diamond just sits at the bottom. The chain never reappears.
@Diamond_Lim I am also stuck at this same level and have tried your suggestions but they didn’t work. I was playing a level past this one on my iPad, but during a game it seemed to glitch, and sent me back to level 4295. I’ve been stuck for several days, but the game on my iphone is on the current level of 4383.