I faced the same issue and I tried the same Apple ID on a different system(If still exists then try it on more devices). The issue is fixed. I hope it will help you.
For more info watch this video(https://youtu.be/L6yptzaQNaE). In this video I suggest 2 solutions.
kkMahesh
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I faced the same issue. I fixed this issue using these 2 solutions
Solution 1: Update your device OS and Developer then try again the enrollment process.
Solution 2: Try on different devices (I tried on different devices with the same Apple ID(If still exists then try it on more devices)).
In my case second solution is works.
I enroll 3-4 accounts using second solution.