I bought an Office 365 Personal 1-year Product Key card on eBay ($30) and tried to redeem it earlier today for 9-months of Office 365 Home on the same account I have used for years with an Office 365 Home subscription (which I still currently have). The system would not let me do so. It only informed me that I would be converting my subscription to a Personal one.
After trying a couple of times, I spoke to an Office customer service agent and two agents in Microsoft Account & Billing Support (the same department that has helped me Office 365 product key redemption issues in 2015/2016. Here is what the last agent in Account & Billing Support said:
“I have verified that our process to allow our users to upgrade their Office 365 Personal to Home has been updated. Option to provide 9 months of Office 365 Home is no longer available. To allow you change/convert/upgrade your Office 365 Personal you can purchase either Office 365 Home monthly or yearly subscription. Our process has been updated just recently. That’s the reason why that option was not given to you earlier.”