When the Activate approval for trips is enabled, the trip requires pre-approval. Just like expenses, this will go to your Approver/Controller for approval before users can link it to an expense.
To enable the Activate approval for Trips as an Admin.
1. Go to Admin > Advanced settings
2. Under the App settings, enable the 'Activate Trips' first, before you can enable the 'Activate approval for trips'
NOTE: If the Controller module is activated, you may opt to set the approval to Approver only or Approver and Controller.
3. Once completed, click Save.