When I run this script, I get chart output that covers the entire period. Check your History folder - maybe you don't have enough historical market data to run the entire simulation that you want.

Also, your stop loss values don't make much sense. You are optimizing over a range of 20-60, which would only make sense for some equity indexes, futures or high-priced stocks. Better to set your stop loss taking into consideration the size of a pip. That way, your script is applicable to individual markets, regardless of the price they trade at. For example, instead of Stop = 60, try Stop = 60*PIP.

Hope that helps.