Not Enough Resources or Space
BuildingCATAN
You may only build when you hold the exact resources for the cost and a legal place for the piece; otherwise the build isn't possible. You may still trade for missing cards during your action phase.
Also answers
not enough resources or spacecan't afford to buildcant affordnot enough resources to buildno legal place to buildcan't buildcannot buildno place for a settlementwhat if i can't build