Sorry for the late reply.
I'm not sure if I understand you correctly: you have placed the code below in your page content?
<?php the_tags('Tags : ', ', ', '<br />'); ?>
This is not working because you normally can't directly use PHP (that's the code) in your page content. You can use PHP in your theme's templates, this is easier if you always want to display the tags at a certain location in your pages.
If you only want to display the page's tags occasionally you may have to look for a plugin which offers a shortcode (which can be used in your content) to do so.
I hope this helps, otherwise feel free to contact me again using this forum.