@TakisM Firmwafe

1.0.3 Build 20201022 Rel 66896

@TakisM 

Do you mean router will lose Internet when RE is plugged in?

You could try a factory reset RE and set it up as AP mode again:

reset: with RE powered on, press the reset hole unitl all the led flashing once 

For" I loose again internet connection on the router (ZXHN H168N)" how about the Led status on router, does the Internet Led go RE or go off? 

May I know your network topology? 

@Solla-topee 

A cable goes directly from router to AP

Router is on. No WIFI is opened on the router, is always closed.

I open the AP

After about 30 secs I loose the internet from the router.

The laptop that is also connected to the router, losses internet.

On the router the light is still green.

On the AP all the lights are green.

I will try the reset, but I do not believe it will change something.

@TakisM Thanks for the details.

Make sure none of the devices in the local network have IP conflict with router. 

Try a different Ethernet cable between router and AP (tp-link)

May I know your network tpopolgy, what are the devices connected to RE, and what are the devices connect to router? (confirm nothing has IP conflick with router)

If possible, you could save router's log after issue happens and share it with us and router support at the same and see what could cause the issue.

Btw, do you have RE220 ， Version 2? Thanks.