@devanirnf Please provide more specific symptoms of the connection problems, like the unstable connection or slow speed. What is the led status of the Archer C9 when the connection problem happened?...

@Stevorama Hello, sorry for the trouble caused here. You can tell us the current problem and then we can do some troubleshooting and try to fix it. Best regards.

@Panditji_N450 Please login to the web UI of the TL-WR940N and go to status page to verify whether it has the valid internet IP address. And please check the operation mode of it, is it wireless...

@Simon1234 You can refer to page 43-44 of the user manual to configure it as the 3/4G router mode. https://www.tp-link.com/support/download/archer-vr900/ With the USB modem plugged into the USB port...

@Neishie Do you use the TL-WR340G to boost the wifi range with the main router together? If so, you can configure it as an access point, instructio as below: https://www.tp-link.com/support/faq/417/...

@B_Ogbrush Do you have any TP-Link device? Generally speaking, the router will be located in an open flat area, while some devices can be wall mounted by the 3rd party tools/accessories. Like Deco....