To enable auto-dedupe for your contacts:
1. Click the Auto-dedupe icon at the bottom right of your table
2. Select Enable automatic deduplication
3. Choose which column to dedupe by (like email address)
4. Click Save Changes
If it's already enabled but not working, try turning it off and on again using the same icon.
You can also manually dedupe by right-clicking a specific column and selecting Dedupe > Delete Duplicate Row.