For this error do the following steps.
- Install latest java.
- Uninstall DSC token driver.
- Uninstall Emsigner.
- Install Emsigner again.
- Now install DSC token drivers.
Restart your system (some time works without a restart).
Now right click on Emsigner icon. Choose Run as Administrator.
Once Emsigner starts. You can sign using DSC.
Exactly same issue was faced by one client and with these steps things worked.
Also add gst.gov.in to trusted sites in you java.