Hi @Lisandra,
rtMedia has recently been updated to improve its compatibility with the new version of BuddyPress (3.0). Do you have the latest version installed on your server ?
If the update does not resolve your issue, can you provide us with a WordPress log file ? To activate logging on your website, just turn WP_DEBUG to true, like following:
define ('WP_DEBUG', TRUE);
You will find this constant in your wp-config.php file.
More on this in the following topic: https://codex.wordpress.org/Debugging_in_WordPress
Cheers,