An empty app list

Every time I refresh, it shows me a dialogue downloading index data and then I get “No repository has package updates” and an empty app list. (My network is fine and I’m on Lollipop on Nexus 5.)

This occurs to several users according to this forum post: https://f-droid.org/forums/topic/i-installed-f-droid-and-manually-updated-repos-but-no-apps-are-listed/