Ikea Tradfri Gateway don't connect to a network

I connect my Ikea Tradfri to a router. All three lights are on, but the App can’t found the gateway.
I use an IP scanner on my Mac, and I can’t found Gateway.
The app suggested that if I am sure that Gateway is connected to the same network (and it is)

I found a solution on the net, connecting Tradfri Gateway on mac, and shared the internet. This way, I can see the Gateway on IP Scanner, but the app still doesn’t work.

What is the problem…