Hi there, I was in the same, I just did that few weeks ago. What I was doing wrong was the UCI number. You have to put the applicants UCI number, not the sponsor's. And the number in the end should be the sponsors+parents+dependants (if your parents has a dependent who you are sponsoring as well). In my case it was me(sponsor)+my husband(co-sponsor)+my parents=4.Could someone direct me on how to link to GCkey. I have tried ++++, unable to link it.
Hope this will help