I got locked out from too many login attempts 2-3 days in a row before I found the magic combination for GCKEY.
The biggest thing is making sure the # of applicants at the bottom is at least 2. This seems counter intuitive if your spouse is the only applicant, but they count the sponsor. If there are dependents, add them on. I even tried 3 a few times because we have a daughter (dual citizen like me) but she didn't count - our number was 2. lol
We lucked out with his passport info... it never did accept his city/country of birth.
Use the Application Number & UCI option. That way there's nothing subjective about it - it has to be those two numbers. The Applicant's UCI, specifically, not the Sponsor's UCI.
You can input the sponsor info into ECAS in the meantime (
https://services3.cic.gc.ca/ecas/security.do ). It's less detailed but updates a little quicker than GCKEY.