I keep on trying to click browse to select my z64 file, but I keep on getting this error

[G64] lua/autorun/client/g64_spawnmenu.lua:31: attempt to index global 'libsm64' (a nil value)
1. DoClick - lua/autorun/client/g64_spawnmenu.lua:31
2. unknown - lua/vgui/dlabel.lua:237

I attempted to type the directory myself, but it doesn't work neither.

UPDATE:

I just had some C++ files missing which is why it didn't work. However, it seems like G64 isn't working properly as it won't load properly on some maps as it has something to do with the cache overflow.