Most importantly, the person setting up the integration should be at least an Editor in Planning Center People.
What about permissions on lists and workflows?
In order to sync a list with Clearstream, the person must have View only or Manage permissions for that list in Planning Center.
Similarly, if you want to use the Push to Planning Center step and add someone who uses your keyword to a Planning Center Workflow, the person must have either Edit all cards or Manage workflow permissions for that workflow in Planning Center.
When you first set up the Planning Center integration, you will log in to Planning Center and grant access to Clearstream. Clearstream will only be able to access the lists and workflows that the person who logs in to Planning Center can access.
If you're trying to sync a Planning Center list or push Clearstream subscribers to a Planning Center Workflow and it isn't working, make sure the person who set up the integration has the correct Planning Center permissions.