LinkedIn

Please check the LinkedIn Application Setup Guide again. Specifically, section 3.4.2 for setting your OAuth2 Redirection URLs:

OAuth 2.0 Redirect URLs - add all variations of your domain along with index.php, as shown below. Replace yourdomain.com with your actual domain name. If you have https enabled on your site, or other ways to access your domain (like www and non-www), add them all here, like:
yourdomain.com/index.php,http://www.yourdomain.com/index.php
If you have multiple ways to access your site (http and https, www and non-www), you need to add all of the possibilities in this box. Please note: You need to comma-separate each value but do not use a carriage return in between URLs. With multiple URLs, it will look like the image below, which is hard to read, but required.

If that setting is wrong for your site, you'll get the error that you're reporting.

I hope that helps, but if you need more help, just let us know.

Thanks,
Alex