async=True

app/app.py

@@ -1083,7 +1083,7 @@ class Originate(Resource):
              'Context':'from-internal',
              'Exten':number,
              'Priority': '1',
-             'async':'true',
+             'async':True,
              'Callerid': '{} <{}>'.format(user, user)}
     app.logger.warning(_act)
     await manager.send_action(_act)