Setting A_UTF16Char to a file path

I'm trying to use AEGP_OpenProjectFromPath to open a manualy specificed .aep

I've tried this with error:

const A_UTF16Char *pathZ = reinterpret_cast<const A_UTF16Char *>(L"/transfer_test.aep");
suites.ProjSuite6()->AEGP_OpenProjectFromPath(pathZ, &my_projH);

After Effects error: Can't import file "var": unsupported filetype or extension. ( 0 :: 1 )

There are no examples that use AEGP_ProjSuite6's IO functions.

Any help would be great. Thanks.