hi dahongfei,

I would love to help you, but I'm not sure what to do.... The chart not loading is probably because it's quite data intensive, so probably your vpn/ssh connection doesn't like that... I could render it all charts server side opposed to client side (what i'm doing at the moment), but the server is not really suited for that. it has trouble keeping up as it is at the moment. So handling rendering the charts will probably result in a slow site for all visitors.
So unless I get some more funds to pay for better hosting the service will be as it is. Feel free to chip in a few bitcoin pennies to the donation address and I will upgrade the web host. Sorry I can help you much further at the moment.

regards Bjorn