Sorry to be right. This is one of those vicious "not my problem" finger pointing circles. But, ultimately if they offered you a free copy of Office 365 Personal, then resolving your mistake when trying to activate the free offer lies with Huawei.
First, confirm if your purchase included a "free" full copy of Office. Look on your invoice and look at that NewEgg listing for the computer. Some say something like you get "1 year free of Office 365 Personal", some say you get a "free trial of Office
365".
Does your email from Huawei include something like a "trouble ticket number", or some other unique identifier for your original contact with them.
If you are supposed to have 365 Personal, try Huawei again. Ask to speak to a supervisor. Front line support people rarely have the authority to fix this sort of problem ("giving away" another product key for Office).
Be prepared to spend a lot more time on the phone.
If you have a lost free offer, the simplest, brute force fix would be to return the computer for exchange, or refund and buy it new machine...