When on the Calendar page, there will be 4 dropdown menus on the top of the page. They will say, from left to right: Categories, Statuses, Venues, and Spaces. You can use any of these dropdown menus to select your filters.
Next to these dropdown menus is a box that says "My Events Only." When selected, the calendar will only show Events that you are the Venue Manager for. If you have Events missing from the calendar, it could be because this box is selected.
In the Events tab, you can edit your filters in the top right corner of the page.