Gerben,
It's likely not the iPad, it's a restriction of LinkedIn. You look to have configured your LinkedIn application to use the URL:
openyourhotel.com
However, your site appears reachable at both
www.openyourhotel.com and
openyourhotel.com. When you go to the www version, the button is missing because LinkedIn can't verify that that is the 'correct' URL for the application.
We recommend setting up a redirect for your site so that all www traffic goes to non-www (or vice versa). If you use an .htaccess file, this is the code we use to do it (forcing www):
RewriteCond %{HTTP_HOST} !^www.sourcecoast.com$ [nc]
RewriteRule ^(.*) http://www.sourcecoast.com/$1 [r=301,nc,l]
To go the other way, simply remove www. from both lines.
There are also extensions for Joomla that can do the same thing, so don't be too hung up on the above solution.. it's just one suggestion.
Hope that helps, but if you run into issues or need more help, just let us know!
Thanks,
Alex