The light is just a little neon that shows whether there is electricity supply on the 'shower' side of the pull-switch.
If there is no light, there is no power at that point, so no chance of the shower working.
Start by looking at your Consumer Unit / fuseboard to see if the shower has a separate supply with its own breaker. If so, see that the breaker hasn't tripped (or fuse blown). If so, replace/reset and try once again. If the breaker trips again there is a fault with the unit or the wiring.
Occasional breeakers trip for no good reason - but it won't happen twice in quick succession unless there is a real problem.