What is your technique for finding the glyphs to begin with?
Went near every building that had them while going after the viewpoints. Once the buildings with the glyphs had been pointed out by the pop-up window, just looked at them from all angles with eagle's eye.
If you failed to notice the red eye in the pop-up, just open the menu and browse the locations in the database, they'll be marked out.
Ok, I started systematically breaking it down since I have no idea what it is. Forgive me since I was going fast I don't remember quite what I did but here you go. The codex was aligned with the 2 missing numbers as the 1st and 3rd number. The last passcode shape was the double triangle, the middle passcode number was whatever the codex indicated, the 1st passcode number was guessed. Hope that helped you guys. (This is for the one that is in Tuscany, looks like mountains and a field on the glyph)