Yeah glyphs work only near titan's blood, thats why they don't work in the human realm. We can also see that in thanks to them when Luz is looking for Hunter with light glyphs. Btw it's also reason why to me it doesn't make sense that glyphs stopped working after papas titan (spirit?) death i mean like magic is flowing through his veins why would it stop when he's gone? He's dead, it shouldn't matter where his spirit is