Trouble with new account: cann't login to Editor, error with Dashboard, no Organization found

So I've created a new Unity account. I was able to assign a Unity Plus seat to that new account. And then there are issues that are bugging me:

- I can't use the new account to login to Unity Editor, it either keeps saying Invalid email or password or just flashes the loading screen.
- I was able to login to the Unity ID page, but when go to dashboard (like https://operate.dashboard.unity3d.com) I got Internal Server Error (I signed out and use the old account, it worked normally).
- At this page: https://developer.cloud.unity3d.com/projects/, I tried to create a new project, in the Organization drop box, there's no organization I can choose despite the fact that it's currently in 3 organizations (1 was created by default when created new account, 1 was assigned by the old account, other I've created to test).

The reason I had to create a new account is that I've using the old one to activate Plus license in a PC and Mac already, now I have a new PC, I just couldn't (or don't know how to???) activate the license using the old account.

So I need your help to use Unity plus in the new PC (either by telling me how without using a new account, or telling me how to fix that new account's problems).

Thank you!!