What's your iPhone model ? Has the warning message disappeared ?

If you are using Archer C7 in AP mode, then C7's DHCP server should be OFF. Thus, the devices in your local network, would obtain their IP addresses from the ISP modem directly. So turn off the C7's...

@Venkatesh. There's no WPA3 support in Archer C60. The Wi-Fi security settings, that should suffice in your case, are:

Altering Duplex settings won't help you, because they affect only wired connections (cable connections), but your issue is with Wi-Fi connections as you stated. On the other hand, I can see that your...

I would go for the Deco M5 from your ISP. ISP modem => AX10 => Deco M5 (in AP mode) connected by cable. Second Deco M5 to your second floor connected by Wi-Fi to the first Deco M5. Keep in mind that...

Your guess is exactly right.