Your FTP credentials does not seem to work.
I’d also like to add here that the warning is not coming from our theme.
That also could be coming from a third party plugin also so please try testing for a plugin conflict. You can do this by deactivating all third-party plugins, and seeing if the problem remains. If it’s fixed, you’ll know a plugin caused the problem, and you can narrow down which one by reactivating them one at a time.
You could also try upgrading your PHP version like the user in another thread.
Lastly, try adding this line to your wp-config.php.
@ini_set( 'display_errors', 0 );
That should be below
define( 'WP_DEBUG_DISPLAY', false );
Hope that helps.