It's possible that if your site uses SSO then some links in Microsoft Office products (Word/Excel/Powerpoint) do not open the correct page. Instead, the login page will load and you will be redirected to the homepage. This is a known issue with Microsoft Office products and their interaction with hyperlinks that are protected by SSO.
To rectify the issue follow the steps outlined in the following Microsoft Knowledge Base Article.
Please note that regardless of the version of Office that you have installed, add the registry key in the exact location that is specified in the article.