We detected a problem in approvals plugin in one of our instances (first time we reproduce it):

When we try to get ANY page's children of our custom content type (there should be only one) from the backend using /rest/api/content/:id/child/:type, we get 404, not permitted... while the addon user seems to have right permissions

We tried on new page, new space, etc. to be sure everything was fresh (space permissions, etc.)

We provide a code sample similar to what we have and the logs we get:

self.getHttpClient(req).get({
    uri: '/rest/api/content/' + contentId +'/child/ac:' + req.context.addonKey + ':' + key + '?expand=body.storage,version'
}, function(err, resp, body) {
   console.log('getCustomContent ' + key + ' for ' + contentId,err,resp,body)
    ...
});

As you can see attached, we get:

{"statusCode":404,"data":{"authorized":false,"valid":true,"errors":[],"successful":false},"message":"No parent or not permitted to view content with id : ContentId{id=15958018}"}