@johneli 

Hi, may I have a screenshot of the Advanced->Status page and Advanced->Network->Internet page on web interface of your MR600?

Besides, those TV, wifi termometer and heater are unable to connect the WiFi at all, or WiFi says connected but no internet access?

And what is the hardware and firmware version of your MR600?

  @johneli 

Hi, if your MR600 is bound to your TP-Link ID and online at this moment, you should be able to login Tether App with your TP-Link ID to manage it remotely.

On the Tether App, you will be able to find the hardware and firmware version on Tools->System->Firmware Update page.

In addition, you mentioned that the tv and wifi termometer cannot find the network at all, please confirm if they can see any other available networks, if they are unable to see any WiFi networks, maybe there are some issue with them, if they are able to see other networks except for the TP-Link WiFi network, when you are there next time, please try to change WiFi channel from Auto to static channel such as 1, 6 or 11 on Advanced->Wireless->Wireless Settings page on its web interface.

  @johneli 

Hi, the firmware version is not the latest one, you could download the latest firmware on the following website and update it manually via web interface when you are there next time:

https://www.tp-link.com/support/download/archer-mr600/v2/#Firmware

If problem still exists, we will still need to check the Advanced->Status page, and also try to change the WiFi channel.

  @johneli 

Hi, it seems that the website in your country didn't publish the latest firmware, please download it from this global site:

https://www.tp-link.com/en/support/download/archer-mr600/v2/#Firmware

Note: Archer MR600(EU)_V2_220105 is the latest firmware.