The most usual cause of this issue could be PHP memory exhaustion or PHP time limit. We recommend that you increase your memory allocated to PHP. To increase it, please edit your wp-config.php file and insert these lines:
define( 'WP_MEMORY_LIMIT', '256M' ); define( 'WP_MAX_MEMORY_LIMIT', '512M' );
You can add it before the line
/*That's all, stop editing! Happy Blogging. */
In terms of the PHP Time Limit, you will need further assistance from your hosting provider asking them to increase your PHP Time limit to at least 300ms.
For further troubleshooting, may we request that you enable the debug mode to figure out what may have caused the issue. You can do this by opening wp-config.php and adding:
define('WP_DEBUG', true); /* That's all, stop editing! Happy blogging. */
When you update the RevSlider plugin, you should see some error output describing the issue in more detail. And we might know why and how we can resolve it.
Please let us know how it goes.