I have the same problem that many other members seemed to have had for some time, and like them I cannot find a solution that works for me! In posts and pages, I cannot centre images I upload, even if text and other items are centred. The image editor displays the images as centred (after selecting centre alignment) but back on the post or page, and certainly on a browser, it remains left aligned.
If someone can help it would greatly appreciated!! I know the problem lies in the css file, but I am unsure of the what coding is required.
Please check out this page as an example from my site: http://www.bushlab.com.au/lab/learning-path/
I use the Amplfy theme.
Looking forward to some help to get this resolved at last.