Hi @lisukup 

May I know if your network topology diagram is as follows:

AX55—router )))((( client devices

(Note: — stands for wired connection,)))((( stands for wireless connection)

1. Follow the correct configuration process outlined in the guide for building an Ethernet backhaul using two EasyMesh routers: How to Build an Ethernet Backhaul Using Two EasyMesh Routers
2. Check the Ethernet cable between the main router and satellite device and try using different cables.
3. If there is a switch or other devices in between, connect the satellite device directly to the main router, bypass the switch.
4. Try using different Ethernet/LAN ports on the main router and satellite devices as the backhaul port.
5. Reset the satellite device and repeat the EasyMesh configuration process. 

  @Joseph-TP 

(Satellite) Repeater RE190 )))((( AX55 (Main Router) ------ AX53 Satellite

On the same cable, there was an IP Camera working before, directly connected to the main router (about 9 meters). Now I have changed the location of the AX53 to another place, with another ethernet cable plugged in, through a simple gigabit switch. I reset the AX53 without success. The only thing I didn't change until now was the port on the main router. Now it's connected to a different port using a different cable.

The OneMesh did not reconnect through WiFi after the fault; it looked like the AX53 was dead.

@edit
before the Reset, i had multiple Offline satelits in my network (in Tether app), only with a random MAC listed

Hi @lisukup ,

Do you mean there is a switch between the main router and satellite router? Did you try to remove the switch and connect the satellite router directly to the main router? Because we need to determine if the problem is with the switch?

In addition, what is the model of your switch?

  @lisukup 
It was not connected before through a switch.
Now i connected it through a switch only to try another LAN port of the main router.
After 2 days i have the same issue.
The swtich model - LS1005G

  @Kevin_Z 
The situation now:

The AX53 is connected to another port on the main router directly, using a different cable than on the begining.
My laptop is connected to the lan port of the Ax53.
The AX53 is "not reachable", but the LAN ports are working normal (the AX53 ist workin now as a lan switch), i get a valid IP adress, the connection on LAN is working normal.
I did the reset - now i need to wait a few days.

  @Kevin_Z after all, i get again the "Not Reachable" mode / state.
I did the reset and connected the AX53 to the network like in the guide.
In addition, i have 220 "other mesh devices" in my network