I thought I would post this - not because I need a solution, I've found out what was wrong - but in case it helps someone else.
The problem was that using Ilustrator to produce an Extrude & Bevel effect on text resulted in the entire text box being filled with a solid background.
See the upper sample in this screen shot:
![chrisnaylor_0-1667464655019.png chrisnaylor_0-1667464655019.png](https://community.adobe.com/t5/image/serverpage/image-id/461192i865A93E900DB9464/image-size/medium/is-moderation-mode/true?v=v2&px=400)
It took quite a while to find the source of the problem.
So, look at the Appearance window shown in these screen shots and the order of the effects shown there.
It turned out that if you specify a Drop Shadow effect before the Extrude & Bevel (as shown in the Appearance Window) the Extrude & Bevel applies itself to the entire preceding Drop Shadow effect which is, in practice, the whole of the text box.
The answer is to apply the Drop Shadow effect after the Extrude & Bevel - and that fixes it, as shown here in the lower Sample (again, see the Appearance Window):
![chrisnaylor_1-1667464682925.png chrisnaylor_1-1667464682925.png](https://community.adobe.com/t5/image/serverpage/image-id/461193i14FA202F9CB1BC8B/image-size/medium/is-moderation-mode/true?v=v2&px=400)
Maybe, that will help someone.