If you go
here and sign in to your GCKey. If you don’t have one you can make an account for the PA. Find where it says “link your application”. If you do that and put which Family Sponsorship, it gives you different options to identify yourself. I did “Family name, Given name, and Date of Birth”. Do it exactly as it is on your passport, so it matches your application. I chose passport for the persona details after that and put that information in and it found my application no problem.
I know a big problem people run into is the number of applicants is PA (you) + sponsor + any dependents. So the value should be 2 if it’s just you and your sponsor. Putting 1 will cause it to not find the app.
I’m not too sure why I can link before I’ve had communication. I guess IRCC has opened it in someway since I have the application number.