I'm having a similar issue. Our company has a Microsoft Partner account, which we use to sign our hardware drivers and submit them to Windows Update. We also enrolled in the CSP program. So, our account already has the "Hardware" and "CSP" programs listed on the dashboard home page.
Now, we want to publish our apps at the Windows 10 Store. In order to do that, we need to enroll in the "Windows & Xbox" developer program, correct? However, when I hit the big button called "Add a program" and choose "Windows & Xbox", I receive exactly the same message as the topic starter.
If I do the same with my personal Microsoft account, I don't receive the error, and the Dashboard takes me to payment options. However, we need to use our existing corporate account (which is already used for hardware driver signing).
Any help?