When loading new game, character spawns in air and falls out of world. Continues to happen after respawning. Have uninstalled and retried several times.

Not able to use lobby command ("unknown scoreboard objective")

Since you closed this yourself, I assume you already solved it, but here are the two things that can cause this:

1. You are in the wrong Minecraft version. 1.16.5 is the correct version for all 5.0 versions.
2. You downloaded master. Make sure to always download the latest release from the releases page which is currently Bingo 5.0-pre1