How to get technical support from ASUS?

[wsedrfv]

At asus.com, I am trying to get support. The first step is to enter my device's serial number.
Asus says "Serial Number is incorrect."
I'm looking right at my device. The S/N is printed right on the device. I enter that S/N when asus.com asks me to. ("Please provide serial number of product to accurately confirm your product type...")
Any suggestions or hints how to proceed?
Asus ZenWifi Mesh router CT8, with constant, unending out-of-memory errors when connected to WAN.

[Blake_ASUS]

Hi there,
If your routers are bought by set,not just one router,
please kindly check the SN on the box for the set, instead of the SN on individual routers.
Thank you.