How to add callouts/balloons to drawing in Alibre??

Drawing was created in 2009. Engineer edited the assembly today and opened the drawing to modify the balloons/callouts and found that he could erase balloons, move balloons, but could not add balloons. The other Engineers looked at the drawing and none of them knew how to fix this situation. Engineer started a new drawing using a new BOM and found I had the same issue - still cannot add balloons. Does anybody know why this happened or how to fix it?

Engineer have also opened the assembly and moved a part to allow it to regenerate and relink to the drawing, but it still will not work. Engineer cannot attach the drawing, as it is too large as an STP file. Any suggestions on how to fix this drawing/assembly would be greatly appreciated