@hectornado Comet Cache is a page caching plugin, which means it captures the output from WordPress and stores that output in a static HTML file, only updating the static HTML file when the WordPress content changes.
For that reason, any plugins that produce dynamic content (such as the Custom Facebook Feed plugin) must take into consideration WordPress caching plugins, either by telling the WordPress caching plugin not to cache the page where the plugin is located, or, even better, making use of client-side JavaScript to dynamically update the content so that the plugin is unaffected by server-side caching.
If the Custom Facebook Feed plugin is not compatible with WordPress caching plugins, you can exclude the page where the Facebook feed shows up by excluding the URI of the page in Comet Cache → Plugin Options → URI Exclusion Patterns. Otherwise, I recommend contacting the plugin developer(s) for Custom Facebook Feed and asking them about compatibility with caching plugins.