Typical initial debug questions are:
1. Are you playing with any mods? If so, do you get the same problem when you fire up an unmodded game? If unmodded games are fine, you probably have a mod conflict or a mod that hasn't been updated for the latest patch. To figure out which one is the culprit is, unfortunately, a tedious, disable-one-mod-at-a-time process of elimination.
2. If not playing with mods (or in response to 1. above, you get the same problem when you fire up an unmodded game), have you tried revalidating your game files through Steam? (Go to your Steam library, right click Civ VI, choose Properties, then the Local Files tab, and then Verify Integrity of Game Cache.)