DPRP stands for DirectPayment RecurringPayments. With the old Payments Pro you had to pay $30/mo for Pro itself and then another $30/mo on top of that for recurring payments. Until you were approved and agreed to the additional $30/mo you would get that error. So what it essentially means is you don't have DPRP enabled on your PayPal account right now.
You mentioned that you already signed up for Recurring Billing. It sounds to me like you're on the new version of PayPal Pro which uses the PayPal Manager and the PayFlow Gateway. This is a separate API from DoDirectPayment or CreateRecurringPaymentsProfile. So they've got you enabled for PayFlow, but you're trying to use the old API.
What you need to do is either re-develop your stuff using the PayFlow API or get PayPal to set you up on Website Payments Pro 3.0, which is the old version that used DDP and CRPP. If you tell them you've already developed everything using that API they should go ahead and turn it on for you so you don't have to redo everything. The thing that could be troublesome is the fee structure of DPRP. Again, it's $60/mo when you get it all enabled, but the new one is cheaper. They can redo the fee structure for you to match what you get with PayFlow, and if you can get in touch with the right person, they will, but sometimes that can be tough.
If you have a bunch of trouble getting somebody to help you contact me directly and I can get you in touch with one of my contacts at PayPal that will help you out.
If you happen to be using PHP you might be interested in my PHP Class Library for PayPal which makes the PayFlow integration very simple if you decide you just want to redevelop your stuff.
If you're interested in a better understanding of the different Payments Pro versions you can take a look at this article I wrote not long ago.