You may find that you don't have any available projects in OpenGround Data Collector.
To fix this, go to OpenGround Professional or OpenGround Web Portal and set the desired projects to Current using "Toggle Current". Current projects will then appear in Data Collector.
Projects must be set to Current by each individual user. It is not a system-wide setting.
In Professional, be sure to click on the "Projects" tab to activate the Grid Tools ribbon.
Current Projects will sort to the top of the grid in Professional. You can also check the "Current" column to confirm the status for a project.