home phone not ringing

My landline is not ringing or it rings once and then doesn't ring anymore.  I see the caller id on my phone and on the tv.  I have reset the modem, there is no call forwarding or numbers being blocked. I can't keep calling every day but it happens every single day.  it was fine for like 4 months and now it happens every single day and nothing has changed in my house.  i have seen other people that this happens to online but there have been no solutions.