Can't sign in from OS 10.8.5 to update to Mojave. I enter the ID and password I use to sign in on my PC, and it doesn't work. Tried many times.

Have an old Air (mid-2013). Can't sign in from OS 10.8.5 to upgrade to Mojave (the first step to further upgrades). I can sign in to the main site with my Apple ID, but when asked for ID and password after clicking the Get button to download Mojave, I enter the ID and password I used to sign into the site, and it doesn't work. Tried many times.

Also, I get verification codes, sometimes every few minutes, whenever I'm interacting with the Apple site, even when there's been no announcement that a verification code has been sent. Sometimes get TWO DIFFERENT codes, one on my phone, one by text. Only one works. Kind of hard to keep track of which one I should input when one IS required.

According to the Mojave page, which was last updated in February of 2022 (twenty-twenty-two), Mojave can upgrade from 10.8, on my hardware (mid-2013 Air). Why can't I?