Unable to connect - Oops, , it seems like there....

Hi,

I have a problem connecting to the game.
I am trying to connect from my computer using WiFi (TP-Link router) and I keep getting the message:
"Oops, it seems like there is a problem with connection to the server.
Server might be down for amintenance, please try again later.
..."

I am trying to connect with my mobile working on the WiFi using the android app and get connectio error as well.

When I switch mu mobile to mobile network, I can connect from the android app correctly.
When I use thetering on my mobile device and connect to it from my computer - I am able to connect to the game.

Is there anything I should define on my router in order to use the game?

I must mention that sometimes it works on my regular WiFi....

Thanks