@Mary-PC wifi signals lose strength when passing through solid objects like walls. The denser the material the worse the effect. In many homes you need more than the single free hub Sky gives you you. They sell an add-on bundle called WiFi Max (see https://www.sky.com/help/articles/sky-wifi-max) which can provide up to 3 wifi extenders. Altternatively you can buy your own wifi kit if you prefer which can work out cheaper over time.
One thing worth trying before spending money is to make sure your hub is in the best position which is out in the open on a surface above obstructions like radiators.
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65inch Sky Glass, 3 Sky Streaming Pucks, Sky Ultrafast + and Sky SR213(white Wifi Max hub) main Wifi from 3 TP-Link Deco M4 units in access point mode
