The most common reason that you will not see an event in your Events or Flexible Opportunities list under the Event Calendars because the event is further than the miles set in the calendar configuration from your zip code. You can have a System Manger check this by the following:

1. Click Edit Dashboard Draft Button
2. Locate your Event Calendar dashboard part
3. Click on the Gear icon
4. Check the Distance from User. Default is 50 miles.

You should be able to find any event, however, by searching for it. To do this:

1.Click on the Search for Event Set the Date Range to cover the day you want to volunteer and enter a city and or state and click Search. 
2. Once you have found the event, click on the "Sign Up" button to the right of the event