thanks god they finally fix it.please uninstall your a10c module no matter it's updated or not.and install it again.then you'll find you can successfully activate your a10c. ENJOY!
old post:These following things are researched by my self.first.like some people who bought dcs a10c on steam and want to activate it on dcs world.but until people already installed it and opened the activate window, they get an error message like this:Invalid Hardware Code. Make sure the Serial Number used is valid for the product you are trying to activate, generate a new Hardware Code and try again. it's not because of your hardware upgrade or even problems with your os but theactivation program(hardware code which created by dcs world's activation program is incorrect).the reason is you can activate it's steam verson successfully because the avtivation program are different version so you get different hardware code.(you can try your own)
until now I did not find any solution.stop trying until they fix it.that's what I want to tell you.