Unlikely, I'm afraid. Every epic or gog game they've repeated has provided the same code, showing up 'claimed'. I haven't seen a repeat of a Microsoft key yet but can't imagine it would be any different. If you're keen, you could always pause your Prime subscription and sub your next month under a different email address. As long as you do it before the expiry of the offer (you usually have a week or two to claim a key iirc) you should be able to generate a fresh code to use on a new Microsoft account.