franch have been going through the same thing. I was advised on the phone when they had no record of me in the system the first time to write to:
Child Trust Fund Office
Waterview Park
Mandarin Way
Washington NE38 BQG
With the following details.
Own details, childs details
Since when we have been receiving child benefits
Maybe child benefit number
I did this and they then had me on the system, still hadn't received anything and each time I called they said it can take up to a month to get the cheque via 2nd class post . I finally talked to somebody who knew what they were talking about and they had sent it to the wrong address after 3 phone calls checking address details etc were correct. So I am now in the 3 wk wait for another. She also said that she would send out a complaint form as I figure they should recompensate you for lost interest on the money that could have been invested all this time.