I have the same problem. HP Pro 3400 with Intel h61 mainboard.
I tried uninstalling and reinstalling the Realtek driver, but that didn't work. I tried rolling back the 1803 update, that didn't work.
I also tried installing a new sound card, Creative Audiogy FX card. The card lists in device manager with an error. When I try to install the driver it say that no device is installed and cancelled out. Spent some time with creative customer support, but that isn't getting me anywhere either.
I also had a com port installed on another PCIe-x port, it quit as well, but there is a USB card installed that hasn't been affected.
It is almost like they disabled the PCIe-x ports altogether.
I can still get sound when Windows updates with its generic driver but I lose the advanced sound functions that are available with the original Realtek driver package.
Fortunately, I can work around this now by downloading direct from Realtek, installing the sound suite and then ignore the nags that there is an updated driver available.