See Events Manager documentation for Conditional Placeholders, section “Nesting Conditional Placeholders” on the very bottom:
It is possible to use conditional placeholders within each other. However, by default Events Manager will only go one level deep, meaning it won’t check conditional placeholders within conditional placeholders. This is due to the extra processing required to acheive such behaviour.
In order to enable further levels of nesting, you need to add a line of PHP to your wp-config.php file:
define('EM_CONDITIONAL_RECURSIONS',2);
The example above will go 2 levels down, meaning you could nest conditional placeholders within another conditional placeholder. If you wanted to nest one inside the nested placeholder, then you need to increase that number to 3.