Error coming up, plugin loads but won't work

[Sign Artist] Couldn't find the required image size for assets/prefabs/misc/artist_dlc/wood frame (unused)/woodframe.large.prefab, please report this in the plugin's thread.

Player:  can't put anything up in a frame using /sil

Amendment:   only a sign frame that comes as part of the Apartments monument can't work.  All signs I can place manually work fine.   Probably a prefab problem.