Dear Dhiman,
Since you know more than anybody about your system, I suggest you always check for small mistakes (like the one I have mentioned) in your own implementation, even though someone else claims they have checked everything.
As I was checking your implementation, I only unchecked “”centered at max power” box in downsampling tab for each of eight the PIN photodetectors and the simulation was run smoothly. Also, I have chnaged the bit rate in decision components from zero to the reference bit rate. I have attached both the modified file and a snapshot of the results of a visualizer. Please check if the problem is solved in your computer too.
Regards