Hey Greg! Thanks for your response. The ban is on my old Xbox account and is permanent and was issued sometime around 2013. I thought I had swapped the email I used for that account for the newer account and logged into it and redeemed the code without realizing it was the older banned account. I've migrated my Minecraft account to a Microsoft account, but they seem to treat the Windows 10 version as a separate game and I do not have access to it.
It's frustrating knowing that permanently banned Xbox live accounts can still redeem game codes. It seems that I've wasted the money/free code completely. Do you know where I could talk to someone at Microsoft directly about this issue?