Can't request download code

A few years ago I bought the PC/mac version of the game, and earlier tonight I tried to request the free download code for the Windows 10 version and I can't do that. This is the only Mojang account I know I have, and I might have downloaded the Windows 10 version once before, but nothing's showing up saying that I can download that version for free. I've tried searching through the Mojang and Microsoft support sites for anything I could find to fix the issue.