@Abbie1990 first thing to check is thst the WiFi signal from the hub is not compromised by its position. Ensure the hub is out in the open aon a surface so its above obstructions like radiators. You may need a longet cable to the ONT or master phone socket as applicable. Ideally the hub should be as central as possible in the property.
Whilst WiFi signals can pass through solid objects like walls they lose power when they do. The denser and thicker the wall the more signal thst is lost. The max hub uses both 5GHz and 2.4GHz WiFi bands to carry data but it is the 5GHz band that carries the most and unfortunately has the higher attenuation so speeds drop. Basically if you live in a property with solid brick or worse stone walls you will inevitably need multiple wifi sources.
Sky like all isos really only guarantee spedds to the hub as they have no control over the customers home. Read https://www.sky.com/help/articles/wall-to-wall-wifi-guarantee this and you will see it is very limited. They will sell you an add-on which can give you up to 3 extenders if required but note the guaranteed speeds shown here https://www.sky.com/help/articles/sky-wifi-max
Depending on your requirements thst maybe a suitable sokution or you can buy third party wifi kit to get faster speeds but it can get pricy.
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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
