You can use either of them, even both if you want to. Just make sure you are using the right name and details. Application number will be the same for you both but UCI will be different for Sponsor and the PA. Sometimes, it might be a technical fault from their side as it took me a while last year to link the application. It showed me the same issue as well but one day, it linked. Try again after checking properly the details, and if it still does not work, raise a webform or Call IRCC.For linking application to gc key , do we use sponsor's information or PA ? I have been trying to link application using PA info as entered in IMM008 and have failed all the time. Just keep saying could not find application. On PR tracker, i am on background checking since Oct 4. Any help would be appreciated.