Hi Paul,
Thanks for your speedy response. I followed your advice. In doing so, I discovered what the real problem was......................ME!

I was moving the cursor to the border of the cell until the wide cross became a small thin cross. Then, I tried in vain to drag and drop the cell. I learned by accident that in order to execute the drag and drop, I must move the cursor to the border of the cell as before, but don't start dragging till I see 4 arrows pointing up, down, left & right.
Then, it works! In all of the web explanations that I'd read, I never spotted this little difference!

Thanks again for jumping on this.