Unable to create User With asp.net membership with username 'icon1'

Whenver i try to create user (with specific username icon1) using asp.net membership  it will return nothing.
Can anybody help me! if the membership provider unable to create user it will return error  'status'. My Error status is also blank.
Membership.CreateUser('icon1','aa', 'test@test.com', 'test?', 'aa', True, Status)



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