DIAGNOSIS The router's time is incorrect, which breaks SSL/TLS certificates for websites. This happens if it can't sync with an NTP time server at boot.
FIX Manually set the router's time zone and force a time sync.
- Log in, go to Administration > System.
- Set Time zone to your correct region.
- Click Apply. Then, under Network Time Server, click Refresh.
- Check that the Current time field updates correctly. Reboot the router.
IF THAT DIDN'T WORK AiProtection's malicious site blocking can sometimes cause false positives. Go to AiProtection > Network Protection and temporarily disable Malicious Site Blocking. If the errors stop, you can re-enable it and add the affected sites to the whitelist.
HEADS UP This error can also appear if you're trying to access your router's interface (router.asus.com) via HTTPS. It uses a self-signed certificate—just click "Advanced" and "Proceed" in your browser. Don't do this for regular websites like Google or banking.