I want to share a fix I stumbled upon after wasting hours Googling and 40 minutes sat in the queue for Apple’s Developer Program telephone support.
If you are getting the error:
You’ve already agreed to the Apple Developer Agreement.
Continue to Member Center or sign out.
No matter what I did, trying to continue on always redirected me to that same page.
In my case, the solution to this was that my email account was not verified. I had signed up to the developer program with a different email to the one registered to my Apple ID.
To fix this, I had to go to the Apple ID management page, log in, and then re-verify / validate my Apple ID.
This isn’t a difficult problem to solve when you know the solution. The frustrating part is that the error message given (or lack of) made tracking down the root cause really difficult.
Hopefully this will save you some time / hair loss in the future.