Can you upload the 2D dwg along with its 3D model
I guess the ref. feature is missing but need to double check with your file
A similar thing is found today. I cannot add into the popup text entry fields. I can add into the dimension properties (left side) area. It has worked before and is very convenient. SWK 2016 SP5.
Update- End SWK, Restart, Re Open the drawing; restored access.