I wanted to buy a race change on retail. Got the screen where I select the character, made my selection and submitted - and then the blue window appears (empty) and the process stays stuck there. True if I try to buy anything else from the shop and also does not work from 2 other computers in the house.
There’s a few things that can cause this, so there’s no one easy solution here, but thankfully we’ve collected them all in our In-Game Shop - Black Screen or Blue Box article! Give it a go, and hopefully you can get your race change going