I have the same problem. New fresh windows 10 install on new laptop. Install enpass from MS store. Use backup file from desktop to transfer data. Now it's just blank.
Uninstall. Reinstall Desktop enpass win32 version. Still blank. Unistall. reboot. run cc cleaner. reinstall. still blank.
OK. Uninstall again. Delete every folder with Sinew or Enpass. Use Regedit to delete every Sinew or Enpass entry.
Reboot. Reinstall Desktop win32 version. Still blank.
Try directly opening .backup file = still blank
Try directly opening walletx file = still blank