Page templates missing in “Page Attributes” meta box after update to WP 4.9
WordPress introduced a caching mechanism to the list of files fetched from a theme in version 4.9. This also leads to the caching of the page templates on page edit screens, in the Page Attributes meta box. When using a child theme, after update to WordPress 4.9 and update of Avada to 5.3 some users had page templates missing from the drop-down.
The issue will get auto corrected after some time, when the cache for files from a theme gets cleared. Unfortunately there is no way to get it cleared instantly. The whole problem is currently classified as a WordPress core issue, is tracked here https://core.trac.wordpress.org/ticket/42573, and will hopefully be resolved in WordPress 4.9.1.
TEMPORARY SOLUTION: In order to get the cache cleared instantly, you can download this small plugin below and install it via WP Dashboard > Plugins > Add New. Click Upload Plugin button and activate the plugin after installation is complete. Plugin name is: Fix for theme template file caching (WP Trac #42573). Finally open a page edit screen. Now all page templates should be available again. Once that is the case, you can uninstall the plugin again.
Credits to Weston Ruter from XWP for creating this code snippet.