@Runner973 Most probably once configured, the RE reports its status to the TP-Link Cloud regardless the Tether app is open or closed.

@Kate_Lin Have you tried to recover your router following this procedure - there's no need of programmer like ch341a to do this.

@Foz203 You can whitelist/blacklist a device with Access Control feature. There's no feature that allows you to limit the users to a certain number.

@henryzusa Can you describe your network infrastructure (what type of devices do you have in your LAN) ? How the WR840N is configured in AP mode - did you use the same guide (I posted) as for the A6....

@jjdneves I'm using no-ip which is still free. Both Synology and TP-Link support this DDNS provider.

@jjdneves I really don't know if the TP-Link support this URL format for updating its DDNS. On the other hand why would you add this custom DDNS, while you can use it in your Archer C9 - that would...