Unable to place Summon Sign in certain areas [Spoilers]

As the title says, I can't seem to place my summon sign in some areas of the game.

I can place my sign: All areas on High Wall of Lothric. All areas in the Undead Settlement. All other areas in the game.

I can't place my sign anywhere within: Road of Sacrifice (all bonfires under that heading, including places like Farron Keep, Farron Keep Perimeter and so on). Cathedral of the Deep (All bonfires, same as above. Cleasning Chapel, etc)

Things I've tried. Making sure I wasn't being invaded/being online. That's about it. Any idea why this is happening?