And since when microsoft need to appove the key before you sell it? I not belive this story It's either msdn keys or you simply not have them or they are just fake keys.
But if you can provide the microsoft coa sticker I will buy 1 windows 10 pro and only via escrow to make sure it's legit and i will call microsoft to check the source of the key and if I get the confirmation that they key is legit i will tell the escrow to release the money!
i sell OEM lisences so having that prices, i assure you all valid and never used, you can do any validation for them but i only accept btc. also made offer in bitify as well
Selling on Bitify is the right way to go, because buyers are protected by a 30-day-escrow.
Good luck!