cannot load source file (.cpp) but can load (.h)

I am able to load .h file but cannot load .cpp file from fetch source files.
.h and .cpp files are stored on same location , I had compiled code with -g
on file browsers left side , I see in yellow mark "Maximum entries in tree below is 300 (hiding 2833)". All files can still be searched for in the input above.

I see my .cpp file in sources file but when I click to load it says that file not found.
I am quit new to gdbgui.