ASUS DSL-N55U does not connect to the router of the provider by LAN

I have a Chinese wi-fi router from my ISP, and I took an ASUS DSL-N55U router for 5 GHz wireless internet. I connected both routers via a network cable, LAN1-LAN1 sockets. The ASUS DSL-N55U router cannot access the Internet. About six months ago, through the same circuit, TP-Link connected automatically. Asus has the admin area working, devices are connected via Wi-Fi, no internet.

Tried different network cables – no result.
Tried different LAN ports – no result. By the way, the LEDs above the LAN ports are not even blinking. Although from the first cable connection (hot) blinked for two seconds.
I switched the provider’s router to bridge mode via admin – no help.
I reset the settings.

Response

The problem is clear. The scheme is simple and everything should work. You want to use ASUS DSL-N55U as an access point. If there is no such mode in the settings of this router, you just need to disable the DHCP-server in the DSL-N55U settings. Save the settings, reboot the router and make a connection between the routers using the same LAN-LAN scheme.

If it doesn’t work, you can try to use ASUS DSL-N55U exactly as a router. Connect the cable from the provider’s router to the WAN-port on the ASUS. In the settings set the connection type to dynamic IP (factory default settings).

Well, and a very important point: does the Internet via cable work from the main router, which was installed by your provider? If you connect it to your computer, for example. Does the main router have a DHCP server (automatically assigns IP addresses)?