Check to see if you have dial tone on a landline telephone plugged into the main telephone socket.
If you do not have dial tone then Reset Router and Sky Glass by switching both off at the mains sockets for approximately 10 minutes and then switch on again
If you do not have dial tone then you have telephone line problem which will require Sky / Open Reach to investigate.
FYI, we are all Customers here and you will need to contact Sky Customer Services to arrange line investigation.
