BuddyPress.org

You need to remove the “- ‘.BPLANG.'” suffix from the .po/.mo files in your bp-custom.php

Use this:

<?php

define( 'BPLANG', 'mysite' );

if ( file_exists( BP_PLUGIN_DIR . '/bp-languages/buddypress.mo' ) ) {

load_textdomain( 'buddypress', BP_PLUGIN_DIR . '/bp-languages/buddypress.mo' );

}

?>