Some plugins and themes are known to conflict with some of the features implemented in Jetpack. Until these conflicts are resolved, you can check this list to find out what to do.
Better WP Security
This plugin can block access to your site’s XML-RPC file. This file is used by Jetpack to connect to WordPress.com, and must be accessible at all times. You will consequently need to configure Better WP Security to make sure that your site’s XML-RPC is publicly accessible.
W3 Total Cache
There are known issues with the Minify engine in W3 Total Cache and many other plugins, including Jetpack. If you experience issues when the Minify engine is activated, try deactivating it to see if it helps.
Antispam Bee, Spam Free WordPress, Bad Behavior, CommentLuv
These plugins are currently not compatible with the Jetpack Comments module.
Cleaner Gallery / Hybrid themes
If you use the Cleaner Gallery plugin or a theme including this functionality, you won’t be able to use the Carousel and Tiled Gallery modules on your site. To solve this conflict, you can install this small plugin to deactivate Cleaner Gallery.
The ComicPress theme is not compatible with Jetpack’s Mobile theme. Comics published via ComicPress cannot be accessed from the Mobile Theme.
CloudFlare is currently not compatible with Jetpack Likes. Like buttons won’t load until you disable CloudFlare.