I hit the D-N-D button on the on the attendant station once to put it into night mode and the same thing happens. I hit the D-N-D buttom again and it started flashing (looks like this means it's in special mode) and the line now rings fine and doesn't go into VM until after the 4th ring. If I hit the D-N-D a third time and to deactivate it the problems starts occuing again. Any ideas on why this is occuring?