I'm not sure I can help, but am curious what system you are trying to create an account with. I get confused because there are at least four different systems that I've used over the past couple of years:
Sign in to your IRCC secure account - Canada.ca - I use Option 1: GCKey to sign into this service. This is the service that I linked our first paper-based family sponsorship application. When I log in now, it only shows our first application, which failed, and one Travel Visa application (also failed). When I linked the paper-based application, I recall that it was also saying something was invalid; it was the number of applicants that was my issue - I think I was entering 2, for my partner and youngest child, but when I entered 3 to include myself, it worked... or something like that, the point is that it is very specific without telling us what specific information they mean for us to provide.
Client Application Status (cic.gc.ca) - I thinks this is also known as E-CAS. When I log in, it only shows our first application, which failed. It doesn't show our current online-based application, or any Travel Visa applications.
Your Application Status Tracker (cic.gc.ca) - This is the tracker that I rely on now. It has our current family sponsorship information, two other failed Travel Visa applications (different from the one listed above), and our failed family sponsorship application. For this service, I created an account with my ID and information, as sponsor; and we created an account for my partner, as applicant. Both provide different information. My account shows that they approved me as sponsor, my partners account shows the status of the various steps that IRCC is completing.
For our online application we used this service:
Sign in | Permanent Residence Portal (cic.gc.ca). The only information on this site is we can download a copy of our application. And it can be used for applying for family sponsorships, PR Card renewals, and PR Travel Documents.
There might even be one more...
The point I was trying to make in response to your question though, is that the responses required to be successful in creating accounts and linking applications are very specific.