Why does getting the site elements not working in headless mode?

I have been trying to utilize a selenium program in python, which works fine. But when i try to make it headless, the program simply doesn't work anymore, as it seems to not find the necessary items on the site.Is this a known issue, or is it just the site that is bugged?

I tried searching for the elements in diferente ways, utilizing XPATH and CSS_SELECTOR, but it still seems to not find the elements on the screen if it is running headless, is there some kind of thing like some javascript on the site that doesn't work on headless because it hasn't been loaded properly?