Hi,
I faced a very similar issue during my enrollment process. I have been trying to complete the Apple Developer Program purchase since February 24th.
During this time, I raised multiple support tickets and contacted both the Apple Developer Support team and the iTunes/Media Services support team. Each time I was advised to wait 72 hours before trying the payment again. I followed these instructions and waited every time before retrying.
So far, I have waited through four separate 72-hour waiting periods, and even after the fourth 72-hour window, the purchase still fails with the same message.
The iTunes support team asks me to contact the Apple Developer team, while the Developer team asks me to contact the iTunes team. Because of this, I seem to be stuck in a loop between both teams.
In my case, I also discovered that when I attempted the payment using a different Apple ID in the Developer app while my iPhone was logged in with my personal Apple ID, the money got added to the Apple ID balance of the account logged into the phone. Unfortunately, that balance cannot be withdrawn and also cannot be used to purchase the Apple Developer Program. It can only be used for Apple services like subscriptions.
You might want to check if something similar happened in your case. You can verify it by going to:
Settings → Tap your Apple ID name → Payment & Delivery → Check the Apple ID Balance.
Hope this helps, and I hope your issue gets resolved soon.