@RachelBA17 if the device is connected by Wifi the issue could be poor Wifi signal level. Streaming video requires both sufficent bandwidth and a signal free from interference. If the device worked without issue before try rebooting your Sky hub which will make it find the least congested wifi channel hopefully not being used by one of your neighbours. Also if you have a slow broadbsnd connection remember UHD video requires around 25Mb/s forceschbstream while HD uses around 10Mb/s so if other people are using the same connection when you are watching that can be a factor.
It is sensible to run a network check the Netflix app contains a useful check in its get help,menu which measures the speed coming into the device. Wifi signals are like light and therefore consider the positioning of both your device and the hub they should be out in the open and wherever possible above radiators and the like. Devices like Sky's Stream pucks and even Amazon's firesticks dont work that well when hidden behindcaxwall mounted TV.
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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
