ax2400 wifi6 certain web sires are not acknowledged

Sires? 

AX2400 is a wifi speed. What is the NG router model# your referring too? 

What web browser are you using?

Happens across different devices? 

What Firmware version is currently loaded?
What is the Mfr and model# of the Internet Service Providers modem/ONT the NG router is connected too?
Be sure your using a good quality LAN cable between the modem and router. CAT6 is recommended. 

What does "not acknowledged" mean?

What happens when you try?

What browsers have you used?