Home phone

Your cable box doesn’t provide dial tone. Your modem depending on model and if your putting your phone into the right port will. Check that your modem has a phone port and that you aren’t trying to plug your phone into an Ethernet port (there’s a difference)

How can you tell if a port is for a phone or ethernet? The Gateway unit has two phone jacks just labeled 1 and 2.

Phone is smaller, Ethernet larger. Look at a phone cord or Ethernet cord for reference