Could not connect in to query from Bex

Hi all,

I have this issues for long times but haven't find out any solutions yet. I am using SAP Design Studio 1.6 running on DELL LATTITUDE E7440 (Win 10 PRO) , and use VPN to connect to server running sap bobi. There is a connection from Bex named DWH_DEV100. When I use cable without VPN, I can still connect to get the query from datasource. Otherwise, when I use VPN, I still see that connection but when I choose Browse to get the datasource , there is error:

Any suggestion for me please! I'm really need to solve this issue.