When I posted my map yesterday I noticed that it enlarged properly if clicked upon, whereas other pictures lately seem not to. So I did a bit of research and bingo, I've solved the problem. Other Blogger bloggers take note.
After you upload the picture, it comes in at the top of the posting and of course you often drag it to a new spot within the text. Yesterday I left the map and the top and it enlarged with a click. If you drag and drop it doesn't. Thankfully there is a way round it. All you have to do is click on the HTML tab,, identifiy the code for the picture (you can't really miss it) and drag and drop the whole of that code.
Aplologies if a) you already knew that or b) if you couldn't care less because you are not a Blogger blogger.