When Tasks are deleted from your MSP plan they will not automatically be deleted from PPO upon the next import. The reason for this is that PPO has the ability to only import selected Tasks based on which Tasks are selected on the Import Task Wizard view page:
When you‘ve added a Task to your MSP plan you will simply have to ensure the Task is selected on the Import Task Wizard >> View page when importing your project plan in order for it to be added to your PPO project plan.
Re-importing project plans
For more information on the mechanisms involved in re-importing your project plan, please see the following FAQ