After creating a custom template, i.e. suspended page, the template fails to load, and instead the default template is used.
Within the "Web Template Editor", after saving the custom template you're unable to preview the template, and also when loading a suspended domain, the default template is used.
This can be caused by the template's parent directories not having the correct permissions. Ensure that the directories listed below are both set to 711 as detailed within this article:
Another possible cause for this behavior is the root user created the template, but the cPanel users are owned by a reseller. This will prevent those users from implementing the template. In order to correct this, the template at /var/cpanel/webtemplate/root simply needs to be copied to the resellers corresponding directory.