What should I do if I don't not get a clean break in my curds?
If you don't get a clean break it may be because:
The temperature may have dropped - leave the curd to set/coagulate a little longer and see if you get a clean break then.
Your rennet has expired or is close to expiry. If it is close to or just past the best before date on the packet the milk may take longer to coagulate, and you may find you have to wait longer.
If it is still not right after checking the above points, you can try adding more rennet in 1/2 or a 1/4 of the amount that you used the first time. Be careful not to add too much, this could cause your cheese to become bitter or too hard.
This problem may also be due to inactive rennet. Keeping your rennet packet or bottle tightly closed, very cold, and away from light when you are not using it will lengthen the rennet’s lifetime of viability.