Symptoms

1. Confluence URL has double slashes e.g. https://confluence.atlassian.com//dashboard.action
2. Clicking on Space Tools will lead you to a Page Not Found. 
3. Unable to export page to PDF & Word. You are redirected to "https://spaces/flyingpdf/pdfpageexport.action?pageId=6947052" when it supposed to be "https://confluence.atlassian.com/spaces/flyingpdf/pdfpageexport.action?pageId=6947052". Basically the Confluence URL/domain is taken off from the full link.
   
   

Cause

Context path is configured as "/". In <confluence-install>/conf/server.xml, you can see the following:

<Context path="/" docBase="../confluence" debug="0" reloadable="false" useHttpOnly="true">

Resolution

Edit <confluence-install>/conf/server.xml and remove '/' from context path. Save the file and restart Confluence for the change to pick up.