An Assistant from support told me to make a post for you guys to validate my gold free trial

Sorry, but support gave you incorrect information. Trials are not given via the forums. If you just bought an Xbox One there should be a 14 day trial code in the box.

As clarified in the support page you need a valid method of payment linked to your account in order to get the free trial:

"Although your Xbox Live Gold trial subscription is free, we need a payment option on file because the subscription will renew to a paid Xbox Live Gold subscription unless you cancel it. You must add a payment option such as a credit card or PayPal to your
account"

support.xbox.com/.../trial-gold-subscription

Two week gold trials can only been entered into your account and be "valid' if you account is under a free membership, not Gold.

The guy from the support chat told me to post it here, even have me a link to the page and said, "Make a new post and maybe someone will be able to help out."

Hello I am sorry but the 14 day free trial of xbox live gold is valid only for a new xbox live user once. If you had redeemed it in the past (2016 or 2017) or even purchased gold at any point in the past the free trial offer becomes null or void. This is
to make sure that users do not abuse the free trial and collect duplicates of it, I apologize if you wish to try it now but my best suggestion would be to purchase a 3 month xbox live card and give it a try that way. They are cheap and easy to use.

Spy

Gold trials can be used by any account that does not currently have gold. It doesn't matter if you've previously had gold.