Send an email to firstname.lastname@example.org with your account details asking for a key transfer or refund to your catalog because you've lost access to it. They should get back to you eventually with steam/origin/whatever keys and an offer to refund any they can't transfer.
I say eventually because when I did it last year it took 5 weeks before they replied to my request. You can try sending it to email@example.com instead, might go faster since that was where the actual key email came from. The several years old directions were to send to the other address though so it may not work.
The text I used for my request:
"I have been made aware that I can regain access to my GameStop purchases, either through a key transfer to another distribution service, or a catalog refund, and would like to get this done as I find myself unable to successfully login using the application."