Every WP Engine site has revisions disabled in its wp-config.php file. When revisions are enabled, our team noticed that performance issues tended to crop up fairly often. Because of this, it is our recommendation to keep revisions disabled in order to assure optimal site performance.
If your site contains existing revisions, please contact our support team from your User Portal prior to migrating or importing your content to avoid a loss of data. Our Support team can help you enable up to 5 revisions for posts. Revisions will be automatically removed after 60 days.
Please note: This is not a retroactive change. It will not add revisions for existing posts automatically, only when you edit them.
The WordPress Codex features a solid article that covers the assorted customizations that one can make on revisions here: