There are two reasons this message may show:
1. Too many people are using your account
If you share your Sky account with friends or family members, they might be watching something at the same time you're trying to watch a video. The number of people who can use the same account at the same time depends on the type of pass you have (see FAQ: How many video streams can I watch with my account at the same time?).
Solution: Make sure no one else is using your account before trying to watch a video.
2. The previous playback was abruptly interrupted
In normal operation, Sky detects when you've finished watching a video. However, if there was an unexpected interruption during playback (player crash, connection dropout, or power outage), the app may not receive this information. In this case, when you try to watch a video again, an additional video stream may be created and counted against your simultaneous streaming limit.
Solution: The error message usually disappears on its own, typically within less than an hour. We thank you for your understanding and patience during this time.