Try running the line test here:
https://www.sky.com/help/articles/broadband-diagnostic-start
You can also run the test via the MySky app on a mobile data connection.
After this has finished and if it reports back all is good click on broadband to run an updated test. If you get amber or red please follow the on screen instructions.
If this is of no help give Sky a call to report it to them.
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