Many thanks. I continued to experiment and dropped on to the solution which is as above. I normally shoot in 1:1 or 16:9 and therein lies the problem. Switched to full-frame and it worked.
I have tried all the above and still can't access a single image as my first image for a multiple exposure. Still get message 'unselectable image'. If however I have made a multiple exposure and saved it I can select this successfully.What I have don...
