SharePoint2013 farm is broken (page cannot be displayed error message) after ACS configuration

Scenario: SharePoint 2013 farm is broken after ACS configuration. Part of ACS configuration involves replacing the OOB STS certificate with custom or self signed cert. But, after replacing the default STS cert with self-singed cert, you may notice that navigating to any of the sites displays page not found error.

At this point you may see following error message in the event viewer:-

An operation failed because the following certificate has validation errors:

Subject Name: CN= providerhosted.app.com

Issuer Name: CN=providerhosted.app.com

Thumbprint: AH65B00PL

Errors:

The root of the certificate chain is not a trusted root authority..

Resolution: Install the cert to "SharePoint trusted root authority", from CA-->Security-->Manage trust.