When attempting to trigger a workflow either through the Start Workflow action, or by updating an item with a workflow, the "child" workflow fails with the error:
HTTP Forbidden to https://SiteURL/_api/sp.utilities.utility.ResolvePrincipalInCurrentcontext...
Access denied. You do not have permission to perform this action or access this resource.
https://SiteURL/_api/sp.utilities.utility.ResolvePrincipalInCurrentcontext?input=%27i%3A0i.t%7C00000003-0000-0ff1-ce00-000000000000%7Capp%40sharepoint%27&scopes=%2715%27&sources=%2715%27&inputIsEmailOnly=%27false%27&addToUserInfoList=%27False%27&matchUserInfoList=%27true%27 Correlation Id: d9b2fff7-fb3c-b3dc-823e-8cfb630f4c0b Instance Id: 9e6a7c9a-8a12-4f5c-813c-fcad6170b3dd
Activate the Site Feature 'Workflow can use app permission'.