Answer:
Probable Reason - Break in filament of electric bulb
Explanation:
An electric bulb might not glow even if it is connected to the cell, possibly because of break in the filament of electric bulb. As, break in bulb's filament implies break in flow of electric current - between electric cells' terminal.
An evident example of this is , a fuse bulb doesn't light up as the current doesn't pass through filament.
