Sometimes, external factors might cause an event to no longer work. For example, a change in time because of daylight savings, or the end of a sale where the event was set to only show during a selected period of time.
If this is not the case, you can check the following with your Developer:
The correct event name is being used in relation to the logic behind the event
The name of the event hasn't been changed (changing the name can break the logic)
The correct context is being used if your event answer uses context
The correct is logic set in place
If there were any recent changes to your website, it's good practice to test your events, as any changes made to the front end code could potentially cause your events to not work.
If you still think there is an issue that is causing your events to not work, please send a ticket to Support.