I don’t necessarily see any errors in that code but you don’t have to do == true. Make sure you have the right field name and you are testing on a post/page that has content in there.
You can also improve/clean up your code a bit. The code below is very readable but be careful not to use it too much or you wont easily see which endif belongs to which if.
<?php if ( get_field( 'field_name' ) ): ?>
This is displayed when the field_name is TRUE or has a value.
<?php else: // field_name returned false ?>
This is displayed when the field is FALSE, NULL or the field does not exist.
<?php endif; // end of if field_name logic ?>
