This issue occurs when you access the DEH with Mozilla Firefox if the electronic certificate is installed only in this browser.
To resolve this issue, install the certificate in the Windows native store.To do this, we recommend that you obtain a copy of the certificate from Mozilla Firefox and import it to Internet Explorer (official Microsoft browser for the Microsoft Windows operating system).
If you have questions about how to make the copy and then import it to Explorer, you may find it useful to follow the steps in the links "Copy the electronic certificate in Mozilla Firefox (Windows)" and "Import a copy of the certificate to Internet Explorer (Windows)” provided at the end of this help section.
For Mac OS X, install the certificate in the Mac Keychains Access.You may also find it useful to consult the help links provided in "Links of Interest", "Copy the electronic certificate in Mozilla Firefox (Mac)" and "Import a copy of the certificate in Safari (Mac) or the Mac OS X certificate store".
Once installed you can access again with Mozilla Firefox.