At 2-4KH/s is going to be a very long time until a block is found.  
According to the CoinWarz calculator, it could take 49395 days to find a block.
http://www.coinwarz.com/calculators/dash-mining-calculator/?h=2.00&p=600.00&pc=0.0&pf=0.00&d=1987.33065543&r=2.92500000&er=0.01090001&btcer=229.72000000&hc=0.00

You could still get lucky and find one sooner!

The reason for a 0 H/s being displayed is due to the small amount of shares being submitted.  The stats processor does not have enough data to come up with a reasonable number.  Try setting a lower difficulty to submit shares more often, see the help section for more information.