Netgear AX12 Unable to register Product Serial No.

You can check the status here https://www.netgear.com/mynetgear/registration/Product_WarrantyCheck.aspx

that will give information when it was registered

Also I would say look at the article and submit the issue with netgear section 

"I am having trouble registering at or logging into my.netgear.com..."

And be sure to send proof of purchase that will speed you're process up with this matter 

https://kb.netgear.com/1160/NETGEAR-Product-Registration-FAQ

How does NETGEAR use my registered information?

NETGEAR uses your registered information to:

• validate support eligibility and hardware warranty
• assist in the support of your home network
• gather general consumer demographics

I am having trouble registering at or logging into my.netgear.com...

Send email to customer.service@netgear.com with:

• the subject line "Problem with my.netgear.com"
• the description of the issue you are experiencing
• your full name and contact information

Our Customer Service team will gladly work to resolve your problem!

I made a mistake entering my serial number or email address when registering...

Send email to customer.service@netgear.com with:

• the subject line "Correcting registration information"
• a description of your issue
• your NETGEAR customer number OR your full name and contact information
• the product model and serial number

My product does not have a serial number - how do I register it?

(Applies to Home products only. Does not apply to ReadyNAS storage products)

If your product does not have a serial number, it has been refurbished.  The serial number is not required to register your product.  Send email to customer.service@netgear.com with:

• the subject line "Register a refurbished product"
• Product name
• Your NETGEAR customer number or full contact information