Why do I have to set up my credit card for sharing services again, even though I already have this credit card stored in my DB customer account?

In order to be able to use the credit card already stored in your DB customer account for sharing services, you must add it once again for technical reasons and authorise it for sharing services. For the purposes of clarity, you should delete the previously saved credit card from your DB customer account. To do so, please proceed as follows:

1. Log in to your DB customer account. 
2. Find the credit card under "Means of payment" and delete it.