I just bought Xanathar's Guide to everything, but when i try to use its features in the character creator, they dont appear. When i go to the marketplace it doent show i bought it. If i try to buy it it says i already bought it

It can sometimes take a little while for brand new purchases to push through the system. Did you purchase through the app, or directly from the website?

I bought it in the app

App purchases notoriously take a long time to go through because they have to go through the App Store before they get to DDB. In future always purchase directly from the website.