I bought the Harley Quinn and Batgirl dlc, Batgirl goes without problems but Harleys dlc is not shown. I reinstalled it several times but nothing changes, sometimes it just says that I have to install it again and 5 seconds later it is installed
really have no nerves for it anymore
A rather unusual problem. I would: restart the device, disconnect from the network, reconnect, log out, log in again, reinstall dlc. If you got it from the xbox store reinstall the whole game.
If it doesn't work then contact Xbox Support. Of course, you can also do this first, it can only take a while to get an answer.