network address not accessible in task scheduler

I am using task scheduler to auto-open a software(we can call it S.exe) programmed by c++, in this software, i copy a file (using CopyFile function defined in WinBase.h) from a local address(such as d:\temp.ini) to a network address( such as \\192.168.73.63\d\tempdata\temp.ini). The D disk on 192.168.73.63 is shared so normally this can be done correctly when S.exe was open manually, but if it's opened by task scheduler, this copy work failed and getLastError Function returns 1326. 

Can anybody tell me why is this happening and how to fix it?

I am not sure this is the right place to ask this question, you can also tell me where i can find more information. Any advice is helpful.