You (or some of your users) seem to have lost any saved portlets appearing on your General tab. It appears to be blank / white where the Overview portlet page should be.
It is inconsistent, some users only have this issue in specific browsers, whereas other users don't have this issue at all.
Release : 15.9
This issue may occur if there are database-related errors in the logs and flushing the Clarity cache is needed.
Flush Clarity server cache (Click on the KB link for steps on how to do this)