your 767 product is not functional, even reading the forum for hours, doing everything, the plane does not fly level, does not maintain altitude. Now I uninstalled MSFS but I forgot to disable the 767, I tried everything but my key is already activated and I can't install it. I would like at least my 767 key to be reactivated, please! New attempet.
Your instructions are confusing, making a claim is complicated.

Have you tried to uninstall the the 764 Captain even though MSFS is uninstalled? You might still be able to do that. I'm suggesting it because it would have been installed to the MSFS\Community folder which might not have been removed during an uninstall.