Still same issue, not enough acid, and keeping it in the fridge slows down the bacteria. If you drain when the pH is low enough, around 6.0, then if you wait some more and put the curd in the fridge, the existing acid will slowly break down those proteins. But if you drain at a high pH, then there's a lot of calcium in the cheese, and it takes much longer for it all to break down. And then if you cold crash it in the fridge, the bacteria are very slow, and there's not enough acid or calcium bonds broken to begin with to get a good stretch. You either need to let it ripen before renneting, and then you can put it in the fridge, or you can let the curd ripen after.
If it's too slow, take it out and leave at room temp or put the bag into warm water. You'll see the curd mass change. It will go from being this solid rubbery mass where you can't even press into it with your finger, to being more bendy, and you can press in and the mass will give and be softer. That softness is the acid doing its work.
Another way to look at it is when you put it in the fridge, the acid levels should be mostly there. As the curds cool, the bacteria will still be active. And more importantly, the acid is present in the curd to slowly break it down. If you put it in the fridge and the curds are at an inadequate level of breakdown, you're just stopping everything, and they can't keep changing fast enough.
Eventually, you will get to a point where it will be really stretchy. It's like Sailor said, you make it and wait. If you want it faster next time, add more culture, and/or let it ripen longer before you add rennet, or let the curd mass sit in a warmer spot after draining.
