Why is WiFi not working?

Question

WiFi

Good evening! I have this problem with my wireless network.
Building 4 floors. A twisted pair cable with the Internet comes in (Softest provider). On the ground floor there is a Dlink switch. Several payment terminals and an administrator's computer are connected to this switch, and a cable to a Wifi router comes out of it. But this router is connected by cables to 3 more routers. The problem is that everything works but only from a laptop. But from an iPhone and from a smartphone to Windows Phone it connects, but there is no Internet. Help me please.

Answer 1

As a thought, then register the DNS servers with your hands in the phones. For example from google - 8.8.8.8 and 8.8.4.4. Well, either see how a working laptop is connected and do it by analogy, or contact the administrator, it will be easier than now and remotely sort out this zoo of routers.