Hi, this looks like an issue with incorrect ownerships on the Kibana x-pack plugin folder. You'll want to remove your Kibana x-pack plugin install first:
sudo bin/kibana-plugin remove x-pack # run this from your kibana folder
Then you'll want to re-install the Kibana x-pack plugin as the kibana user and setup correct ownerships. For that, follow the instructions here: https://www.elastic.co/guide/en/kibana/current/_installing_plugins.html#_installing_plugins_with_linux_packages
Finally, you'll want to run Kibana as the kibana user. Currently (looking at the output of ps -u | grep kibana it is running as the ec2-user.
Hope that helps,
Shaunak