Adding on to what le helpful floof has already stated above ~
Depending on where you downloaded the markings , Make sure you didn't download anything extra , ( i.e adfly ) for that can cause some issues as well as well as making sure that those are the correct markings you wish to use. And as Kynvuu already said, Make sure that the markings.CFG file is replaced when you copy & paste ( or drag the file ) located in the main Feral Heart folder and the markings are put in media > textures when you copy & paste.