I'm unable to use the Account Transfer option on my user.
A vault transfer can only be performed if the user is in a role that has this feature enabled and has accepted the account transfer acknowledgment pop up. This pop up isn't necessarily asking for user's consent, as there is no way to opt out. If a user chooses 'later' the pop up will simply appear the next time the user logins to Keeper. They have exactly 7 days to accept this acknowledgment; otherwise, their account becomes blocked. Of course, as Keeper Admin, you can extend this notification an additional 7 days, ultimately forcing the user to either accept the popup or continue to stay blocked, making keeper unusable for them.