Since you can insert it from the menu, I take it you mean that the floating pop-up tool-tip is not displaying.

First, you can use the F3 key. You type the name of the AT entry (or at least 4 unique characters from the beginning of the name) and press the F3 key. Your AT will insert.

Or, you put the AT entries into the attached template for a document or into the normal.dotm template. I suspect that in your upgrade the linkages between existing documents and their templates was broken. You can repair that linkage under the Developer Tab on the Document Template button.