Rarely it can happen that the previews are not shown in Microsoft Explorer.
This download (RegisterShellExtensions) contains a zip file containing a batch file that you can place with the EasySIGN application. After that you can right click on the batch file, let it run and choose “Run as administrator”. Then the EasySIGN shell extensions are registered again. After that, the EasySIGN previews work again in Windows Explorer.