Things you want to look at when having problems with your NavMesh:
- Set Navigation System settings in your Project Settings (make an Agent if one doesn’t exist)
- Set Navigation Mesh settings in Project Settings
- Ensure RecastNavMesh object in your level matches these settings
- Ensure CharacterMovement components match those settings
- Try moving the NavMesh Bounds Volume around
- Or, Selecting everything in the level and moving it around has also fixed problems for me.