How are you debugging this? How do you know that you have received the first byte? Do you have any idea how many of the 16 bytes you receive? Do you not get past that while loop or is the data received incorrect? We need to know what all you have done to debug the problem. Also, I would change the second while loop (and the first for this matter) to check the condition like this:

 while (PtrRx < &CompDataRx[16]); 

The condition on the while loop right now is easy to get stuck if your code somehow misses the condition where it is exactly equal to the last element in CompDataRx.