Users being erase

Hi!
I’m having some issues with my users, I have a website that sells products and courses and I need my costumers to be able to access any time on the website, but it seems to be erasing old users. I’ve recently recived an email from a purchase from 2020 and the user was unexisted. Can you help me solve this problem? I used to have configurated not to be erase but now I can’t find that option again.
Thanks!

The page I need help with: [log in to see the link]