Call session#setup method

frontend/app/routes/application.js

@@ -0,0 +1,10 @@
+import Route from '@ember/routing/route';
+import { inject as service } from '@ember/service';
+
+export default class Application extends Route {
+  @service session;
+
+  async beforeModel() {
+    await this.session.setup();
+  }
+}

frontend/ember-cli-build.js

@@ -14,6 +14,9 @@ module.exports = function (defaults) {
         },
       },
     },
+    'ember-simple-auth': {
+      useSessionSetupMethod: true,
+    },
   });
 
   app.import('node_modules/jquery/dist/jquery.slim.js');