I have been mining with 600MH/S and the last block was found three days ago. I guess difficult has been raised to new level used to at least one block per day.
600MS/s - What are you mining with? Config?
That's only like two Ryzen 1700 cpus...
I am using AMD Ryzen Threadripper 1950X 16-Cores and 30 threads 3.4GHz. But, I am only using 25 threads ar the moment. It can go higher with the max 30 threads.