Your water level gauge glass may not be reading properly if it is leaking.  The water level may be higher in the glass than in the boiler when the glass leaks around the top packing nut or top valve stem.  This can lead you to think the water level is good when it is too low.  The low water cut-off may be in safety shut down even though the level gauge looks OK.

Regularly scheduled maintenance will prevent gauge glass leaks.  Advanced Boiler carries a complete line of gauge valves, glass, and gaskets.