windows 8.1 Pro 64 Bits (6.3, build 9600).
Manufacturer: ASUSTek COMPUTER INC. Model: P8B75-M LX.
Intel Ivy Bridge Chipset Rev:09, Intel P75/B75 SouthBridge Rev:04, Nuvoton NCT6779 LPCIO.
Try disconnecting your PC from the internet>close Windows Update>reopen windows update and see if an install (not download) button is showing and click it. Then reboot and start downloading the next batch. Sometimes Windows needs to install what it has before it can download and install the rest. You might have to do this a couple of times. Windows also (like recently) has to update Windows Update before it can further download.
Sometimes the progress bar is not working properly and will show no progress. Sure thing to check if it is actually downloading is to open the folder: C:\Windows\SoftwareDistribution\Download. This folder is where the updates being downloaded to.