Ans:
Syracuse and Pitt have played 70 times total. Sixty of those have been in every season since 1955.
The Virginia vs Virginia Tech rivalry goes back to 1895, and totaled 96 contests. They haven’t met every year, but since 1970 they haven’t missed a season, bringing their current streak up to 45 consecutive seasons.
Miami and Florida St have played 46 of their 59 total games consecutively since 1969 to the present.
Georgia Tech first played Duke in 1933, and have played every season since that first one without missing a single season, now 82 consecutive.
Clemson has played NC St. more times than Georgia Tech has played Duke (83 vs 82). They first played in 1902, but have occasionally missed some seasons, including the 1969 and 1970 seasons. So their current streak of 44 games began in 1971.
So the answer: Only Clemson and NC St have not played every season since 1970.