I've recently implemented your private messaging on a classified listings theme. So that when you're on an age page the sidebar shows the shortcode. However the button shows "> below it (see screenshot aswell). And I'm not quite sure what went wrong.
<button class="btn btn-default btn-lg berichtbutton"><span class="berichtbutton" href="<?php echo $pmshortcode ?>"></span></button>
As for what's in my string:
<?php $pmshortcode = do_shortcode('[pm_user user_id="'. get_the_author_meta( ID ) .'" subject=""]'); ?>
Now I'm an absolute beginner in coding so it might just be me making a dumb mistake. Kindly awaiting your reply!