The Location Selector determines which locations are displayed in TRIP. Click on the down arrow to open the selector:
Open Location Selector
Once open, you can select or deselect your desired locations.
Keep in mind that only selected locations will be displayed in TRIP. This includes tows, accounts, etc. If you can't find something that you're sure should be in TRIP, make sure you have that location selected.
Selected locations are not saved when you log out or exit TRIP. You can set the default locations you want by going to Settings -> Default Locations. These locations will be saved and automatically selected whenever you log in.