When doing Enterprise Portal development, it might happen that when you are going to say Edit on the SharePoint page, you will not see it in editing mode with all the web parts available for editing or adding new ones: the web parts "boxes" are not displayed.
If this happens, one things that worked for me, after spending several hours not understanding what is wrong, is to check the browser you are using and its version. I am working solely with Internet Explorer when doing EP SP development, but, this time it was the version as well. If you are on version 11, you might have to go to Tools -> Compatibility View settings and add your EP address there. It should work.