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The administrator will have either preestablished an ArcGIS account for you to use, elected to allow you to associate an ArcGIS account to use with the organization (for example, by registering an existing account), or invited you to join with your enterprise login. If the administrator later removes your account from the organization, your maps, data, and groups stay with the organization and can be reassigned to other members. If you joined with an ArcGIS account, your account is removed from the system and you can no longer access it, even if it was one you had established before joining the organization..
Hello, I got a very simillar issue (6 years after [facepalm]). Purchased ArcGIS Desktop Personal License, received an activation link from Esri, followed it and clicked on "Activate Subscription". Tried to sign-in with my existing account info in order to move from Public account to Organizational account. Every time got an error "An error has occurred. Please try again later."
The only difference is that my activation window appears in Chinese, it's quite a pain since I'm not Chinese, I did register my Esri Public Account when I was in Beijing, but in my settings everything is in English.
Thanks for sharing, good to know that I'm not the first one with this issue.
Waiting for Esri Support to reply now.
I am having a similar issue and its beyond frustrating - waiting on esri support to assist.