I had that same issue.
There is a question "how many people are on this application" or something like that... I kept using "1" and so couldn't link. Just change your response to "2". Cos it adds your spouse and yourself as 2 people for the application.
Try that and see if you can link it.
Exactly. It took some time before I was able to link the application to the GCkey but don't give up. You'll get through.
Let's keep hope alive, we would all get through soon.
N.B: I got some important info on how and where to book a ticket as well as booking covid-19 test at government approved facility. If you do need these info, you can kindly reach out. Every little helps!