@Eugene29 

Can you please be more specific about the disconnect issue you are experiencing? Is it the WAN disconnecting, or 2.4G wireless, or 5G wireless disconnects?

If it is the WAN/Internet disconnects on the router, please confirm if you have a stable connection all the time with the ISP modem before and after the router firmware update. BTW, who is your ISP?

If it is the 2.4G or 5G disconnecting, please check if you can modify the wireless basic settings on the router, try to run a Wi-Fi analyzer to find a clear channel for the 2.4G/5G network, then change the 2.4G channel width to 20MHz, 5G to 40MHz, change the security to WPA2-PSK/AES, reboot the router and reconnect to the wireless network, then confirm.

@Eugene29 

Firmware update was the only change in the network? If that is the case, please reset the AX20 to factory defaults by logging to its web interface page, then reconfigure it from scratch, confirm again if the internet connection will be stable.

@Eugene29 

As per the release note on the official TP-Link website, this firmware cannot be downgraded to the previous version:

https://www.tp-link.com/support/download/archer-ax20/v1/#Firmware

However, please don't worry, we will help with the disconnect issue on the current firmware, do respond the email we sent to you.