@drdas82 

Hi, for the issue, we would like to check the below information:

You have three powerline units in total, adapter A is connected to the main router by cable, adapter B and extender C, right?

May I know if the PC which is connected to B can get stable connection or not?

If not, please connect a computer directly to the main router by cable and confirm the router is stable. 

If the issue only happens on extender C, can you check if the power saving mode is enabled?

If so, please follow the instruction to turn off Power-saving mode on powerline devices：https://www.tp-link.com/support/faq/2018/

Try different wall sockets for extender and make sure it is away from home appliances to check if the issue happens again?

If so, please put powerline units into the same room and test stability and if the issue will happen again?
 

If the issue persists, please let us know your testing results in details, and help confirm some information:

1. What are the symptoms of the issue, for example, PC or wireless clients connect extender's Wi-Fi but no internet OR can't connect this Wi-Fi at all?

    How often does the issue happen?
2. If House Led is On when issue happens, please check the IPv4 address and gateway and send us a photo on your PC which is connected to the extender's Wi-Fi when the issue happens.  https://www.tp-link.com/support/faq/838/
Please ping the default gateway and send us the ping results：https://www.tp-link.com/support/faq/425/
3. How many end-devices connected to powerline units by cable or by Wi-Fi and what are they, like PC, laptop or smartphone, Windows or mac? 
4. May I have the hardware on the back label of the powerline unit and photo of the firmware version on tpPLC Utility? 

BTW, AV600 is not the correct model number. Please check again. It should begin with TL-WPA.

Thanks for helping us with the troubleshooting!
Good day!

@drdas82 

Good day.

Thank you very much for your kind reply.

The username and password should be admin/admin by default if you haven’t changed that.

Since there is no power-save mode on the wireless power-line extenders TL-WPA4220, only on the wired adapters or the master unit TL-PA4020p KIT, so we can skip the power-save mode suggestions;

So as for your previous issue, could you please check one more details：

1. When it randomly stopped producing a Wi-Fi signal, the Wi-Fi light is on and none of the devices could detect the wireless network of the power-line extender, right?
2. May I know how long have you had the devices and when did this issue start?
3. And if you are not on the latest firmware TL-WPA4220(EU)_V4_190326, please refer to the following link to perform an update: https://www.tp-link.com/uk/support/faq/1614/
4. Have you ever tried to reset the TL-WPA4220,by holding the reset pinhole for 10s to see if that helped?

Thank you!