Unable to register RT-AX92U routers

[ngek]

System: ASUS AX6100 WiFi 6 Gaming Mesh Router (RT-AX92U 2 Pack)
Battery or AC: AC
Model: RT-AX92U 2 Pack
Frequency of occurrence:
Reset OS:
Screenshot or video:
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Detailed description：I am having issues with my AX6100 routers but cannot register them on the site because it does not accept the serial number. Picture attached.
The routers worked fine for the first month but now have intermittent issues with connectivity on both the wired and wireless interfaces.

[Blake_ASUS]

Hi there,
If you about the router by set, please register the product by the set SN instead of individual SN.
It should be on the box.
Thank you.