The issues are reported to have began at around 7am today, July 28, and are affecting people in several parts of the country.
The website istheservicedown.co.uk reported a peak of around 175 reports of problems in Sheffield earlier this morning.
It added the latest reports from users having issues in Sheffield came from postal codes S6, S2, S10, S8, S20, S11, S7 and S21.
Sky tweeted last night it would be carrying out planned maintenance work in Yorkshire and the Humber in the early hours of today, but Sheffield was not one of he interchanges it said would be impacted. Officials said they were not aware of problems in Sheffield.
A Sky spokesperson said: “We have now resolved the issues affecting some Sky Broadband and Talk customers in Norfolk and Suffolk. We're sorry for any inconvenience this may have caused.”