How to Connect to a Specific / Different Region
Sometimes other regions of the game (beyond the default ping limit) will have more players. While a higher ping will be less good of an experience for you, especially outside of co-op (actions may seem more delayed, or things won't hit when you wish they would), this can be an effective way to find players when things are slow in your region.
To configure a different region, from the Main Menu, go to Settings --> Gameplay --> Region, and select a different region from the dropdown:
Consider the time in these regions, there are likely more players where it is a more active time (afternoon/evenings on weekdays).