Landscape Visibility rool Wont work ?

Hello,

I want to build a cave on my map and wanted to use the Visibility tool like i did on my other map to mape a hole…

but it didnt work… when i try to walk throu the hole it like i run againste the wall but i can look throu it…

i tryed the tool on my other map and it worked :frowning: any ideas why it whont work here ?