We have checked your account and see that you have two subscriptions (Creative Cloud All Apps and Adobe Acrobat Pro) listed on your account. Creative Cloud All Apps includes the Acrobat Pro subscription. So, there is no need to purchase it separately.
It is not possible to use two individual subscriptions for the same product under a single account. You can use only one subscription at a time.
In this case, I would suggest you cancel your Acrobat Pro DC individual subscription. Or you may purchase it using a different email address.