I have the same problem as well, running 2.7 with one additional user plugin, don’t think that is the cause of the problem though.
No data is inserted for the user in user table so not able to login using new user id. Checked verification email an no user id entered on that either, the create email to the administrator has the user name but not the verification one.
Not able to modify username after registration either.
Anyone got a fix yet or does this not work on 2.7 yet
