I have similar issues which brought me here to write a post but this was already here.
Try reloading the store over and over, it works for me. Go to store, it stays black, click home then store again, it may say session has expired but then will actually load. The same goes for the categories once you are in the store. Click one, stays black, click a different, it loads, click the one you actually want again it may load. Same for purchases. Look at your ip/rp before you try to purchase something. If it works great, if it cliches then you can start over but make sure you werent charged for something you didn't receive. It took 2 tries for me to buy a rune page.
Also don't forget the sales don't start until the 23rd. I'm dumb so I bought a rune page thinking I would get 2 for the price of 1, which isn't even how the announcement described it anyway=(