Thanks for this. it works!There are some tricks when you try to link the applications. The info you type in needs to be exactly the same as the one you provided in your application form even the capital letters, space, etc. You only choose one of the birth place and the passport info. Now the most tricky part is the number of people in your application. It should be: sponsor (+ co-signer if there is any) + applicant (+co-applicant if there is any), in any case, children are not counted. But it is not always working, so try from 2 to whatever number you used in your package.
Good luck!