Download and install the recent SDK from asset store. Now, 13.0 version.
Bug.01. Can‘t log in google account in Unity Hub/asset store
I’ve also had that problem. But the solution I found was really amazing. When you are on asset store screen(works only in unity editor, not in the hub) just type register, the window will be directly in asset store(not the message box window). Then tap “I have an account”, log in and it will work.Work!