@Bianca1vz when you checked your internet speed did you do so on the TV? If you didn't there is a useful network test in the Get Help menu of the Netflix app. You need roughly 30Mb/s to watch in UHD around 15Mb/s for HD.
However bandwidth is only half the story as interference can cause packet loss and thus buffering. The most common issue is a neighbour's network on thecsamecor adjacent Wi`Fi channel rebooting your Sky hub will cause it to try and find a less congested channel to use. The best long term solution though is to improovevthe WiFi signal in your home either by paying for Sky's WiFi Max bundle which can getvyou WiFi extenders or to buy your own WiFi equipment. If you plan to stream video either can beca good investment.
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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
