The most likely reason is becuase you have not toggled on preview as @ClockworkOcean mentioned. I believe the panning will start working if you hold down the left mouse button in the small material editor viewport window.
The most likely reason is becuase you have not toggled on preview as @ClockworkOcean mentioned. I believe the panning will start working if you hold down the left mouse button in the small material editor viewport window.