This got 7.3.1 working for me:
ATaleikis May 3, 2016 2:34 PM
Everything is much more simple... Do not cancel anything, open AppStore, then click on the "Store" in the top-left menu and choose the following option - "Check for Unfinished Downloads...". Enter your Apple ID and password and you everything will be up and running.
The reason is that XCode does require additional confirmation before download.
Hope that helps.
Yours Sincerely,
Arturas Taleikis.