Unable to use "Edit with existing Vim" option on Windows to open another file

Hi,

    I have Vim 8.0 installed on my laptop which has Windows 10 Pro (64-bit OS).
Suppose in gvim window test.c file is opened currently.
Now when I try to open a file say vector.c in Windows explorer by right clicking on it and
using "Edit with existing Vim - test.c" option, it simply does not open the file vector.c
In gvim window it still shows the test.c file only.

Any ideas for the fix ?

Thank you.
Mahendra