After the ‘Restarting Mattermost’ step, i see the errors (mainly Nginx related). And subsequently, the url (for the configured application) doesn’t work.
Can you show us the contents of your Nginx error log? It would greatly help in identifying where there may be issues in the build/documentation steps for deploying in the cloud.
(You can print the contents of the Nginx error log file to console using the command sudo cat /var/log/nginx/error.log