My yahoo account doesn't remember a common email address I use

Hello,
For some reason the most commonly use email address that I use, I now have to manually type it into my yahoo account when I'm sending an email to this person. It use to retain & I only had to start typing the address & it would use predictive text, which I would just click onto to proceed.
I've made use its in my contact list which it is. I've used it for years. Now yahoo doesn't acknowledge it. Has it been hacked? What can I do to bring it back into the memory of my yahoo account?
Thanks.
Sue