Many of the topics in Explore are location sensitive. So you could be in a particular area where no movies were filmed, so the 'Movies Filmed Nearby' topic will not show up until you get into an area that has movies marked as being filmed there.
All of the topics in Explore are curated by us. Some have specific dates at which they will be shown in order to be relevant. For example we only show a topic on New Year's Eve a few days before and after New Year's.
We're planning on adding support for saving your favorite or most interesting topics in an upcoming release.
If no topics are showing up after a period of time, please let us know by e-mailing firstname.lastname@example.org.