Earlier today, I was in one of my Stack Exchange profiles, and it asked me to fill some new data for new profile: job, tags, and if I'm currently looking for a job.
And an hour later I checked my email and see an invitation there to careers.stackoverflow for my firstname.lastname@example.org email address. Which looks like a smooth transition from my previous actions. But, I already have a profile at Careers on my main Stack Overflow profile linked to email@example.com. And when I follow the link, it automatically logged me in, and I see my name on top of the page which asks me if I want to accept invitation.
I think the problem here, is that I originally create that profile with email firstname.lastname@example.org, and later switch it to have email@example.com as the main contact email. So it looks like systems that sends invites checks only original emails Careers profile was created with, but it should probably check all emails linked to a Careers profile.