One possibility could be my use of wp_get_active_and_valid_plugins
, which does not return “network” plugins on multi-site setups. Inside of jetpack.php
(the one inside of the Send to Kindle plugin, not the Jetpack plugin) try changing line 19 from:
$share_plugin = preg_grep( '/\/jetpack\.php$/i', wp_get_active_and_valid_plugins() );
…to something like this:
$share_plugin = wp_get_active_and_valid_plugins();
if ( is_multisite() ) {
$share_plugin = array_unique( array_merge($share_plugin, wp_get_active_network_plugins() ) );
}
$share_plugin = preg_grep( '/\/jetpack\.php$/i', $share_plugin );
Let me know if this helps.