the root of the issue

The underlying cause or fundamental essence of some issue, problem, or difficulty at hand. Our team of professionals will walk you through a troubleshooting process that will help get to the root of whatever issue you're experiencing with your device. Here's the root of the issue, Bill—we feel that you haven't been meeting the standards of work that we expect of you recently. If the politicians in Washington would stop all their games and mudslinging for a minute might actually be able to solve the root of the issues affecting our country.